LIBRARY 

OF  THE 

UNIVERSITY  OF  CALIFORNIA. 


Class 


CONCRETE 
CONSTRUCTION 

METHODS  AND  COST 


NET  BOOK -This  Book  is  sup- 
plied to  the  trade  on  terms  which  do 
not  admit  of  discount. 

THE  MYRON  C.  CLARK  PUBLISHING  CO. 


NEW  YORK    AND    CHICAGO 

THE  MYRON  C.  CLARK  PUBLISHING  CO. 
1908 


CONCRETE 
CONSTRUCTION 


METHODS  AND  COST 

• 


BY 

HALBERT  P.  ^ILLETTE 

M.  Am.  Soc.  C.  E.,  M.  Am.  Inst.  M.  E. 
Managing  Editor.  Engineering-Contracting 


AND 

CHARLES  S.  HILL,  C.  E. 

Associate  Editor,  Engineering-Contracting 


OF  THE 

I   UNIVERSITY 

OF 


NEW  YORK   AND   CHICAGO 

THE  MYRON  C.  CLARK  PUBLISHING  CO. 
1908 


COPYRIGHT,  1908 

BY 
THE  MYRON  C.  CLARK.  PUBLISHING  Co. 


PREFACE. 

How  best  to  perform  construction  work  and  what  it  will 
cost  for  materials,  labor,  plant  and  general  expenses  are  matters 
of  vital  interest  to  engineers  and  contractors.  This  book  is  a 
treatise  on  the  methods  and  cost  of  concrete  construction.  No 
attempt  has  been  made  to  present  the  subject  of  cement  testing 
v.hich  is  already  covered  by  Mr.  W.  Purves  Taylor's  excellent 
book,  nor  to  discuss  the  physical  properties  of  cements  ant. 
concrete,  as  they  are  discussed  by  Falk  and  by  Sabin,  nor  to 
consider  reinforced  concrete  design  as  do  Turneaure  and  Maurer 
or  Buel  and  Hill,  nor  to  present  a  general  treatise  on  cements, 
mortars  and  concrete  construction  like  that  of  Reid  or  of  Tay- 
lor and  Thompson.  On  the  contrary,  the  authors  have  handled 
the  subject  of  concrete  construction  solely  from  the  viewpoint 
of  the  builder  of  concrete  structures.  By  doing  this  they  have 
been  able  to  crowd  a  great  amount  of  detailed  information  on 
methods  and  costs  of  concrete  construction  into  a  volume  of 
moderate  size. 

Though  the  special  information  contained  in  the  book  is 
of  most  particular  assistance  to  the  contractor  or  engineer  en- 
gaged in  the  actual  work  of  making  and  placing  concrete,  it  is 
believed  that  it  will  also  prove  highly  useful  to  the  designing 
engineer  and  to  the  architect.  It  seems  plain  that  no  designer 
of  concrete  structures  can  be  a  really  good  designer  without 
having  a  profound  knowledge  of  methods  of  construction  and 
of  detailed  costs.  This  book,  it  is  believed,  gives  these  methods 
and  cost  data  in  greater  number  and  more  thoroughly  analyzed 
than  they  can  be  found  elsewhere  in  engineering  literature. 

The  costs  and  other  facts  contained  in  the  book  have  been 
collected  from  a  multitude  of  sources,  from  the  engineering 
journals,  from  the  transactions  of  the  engineering  societies,  from 
Government  Reports  and  from  the  personal  records  of  the 
authors  and  of  other  engineers  and  contractors.  Tt  is  but  fair 
to  say  that  the  great  bulk  of  the  matter  contained  in  the  book. 


17302B 


iv  PREFACE. 

though  portions  of  it  have  appeared  previously  in  other  forms 
in  the  authors'  contributions  to  the  technical  press,  was  collected 
and  worked  up  originally  by  the  authors.  Where  this  has  not 
been  the  case  the  original  data  have  been  added  to  and  re- 
analyzed by  the  authors.  Under  these  circumstances  it  has 
been  impracticable  to  give  specific  credit  in  the  pages  of  the 
book  to  every  source  from  which  the  authors  have  drawn  aid. 
They  wish  here  to  acknowledge,  therefore,  the  help  secured  from 
many  engineers  and  contractors,  from  the  volumes  of  Engineer- 
ing Xews,  Engineering  Record  and  Engineering-Contracting, 
and  from  the  Transactions  of  the  American  Society  of  Civil 
Engineers  and  the  proceedings  and  papers  of  various  other  civil 
engineering  societies  and  organizations  of  concrete  workers. 
The  work  done  by  these  journals  and  societies  in  gathering  and 
publishing  information  on  concrete  construction  is  of  great  and 
enduring  value  and  deserves  full  acknowledgment. 

In  answer  to  any  possible  inquiry  as  to  the  relative  parts 
of  the  work  done  by  the  two  authors  in  preparing  this  book, 
they  will  answer  that  it  has  been  truly  the  labor  of  both  in 
every  part. 

H.    P.    G. 

C    S.    H. 
Chicago,  111.,  April  15,  1908. 


TABLE  OF  CONTENTS. 


PAGE 

CHAPTER  I.— METHODS  AND  COST   OF  SELECTING  AND  PREPAR- 
ING MATERIALS   *  OR    CONCRETE 1 

Cement:  Portland  Cement— Natural  Cement— Slag  Cement— Size  and 
Weight  of  Barrels  of  Cement — Specifications  and  Testing.  Sand:  Prop- 
erties of  Good  Sand — Cost  of  Sand — Washing  Sand;  Washing  with 
Hose;  Washing  with  Sand  Ejectors;  Washing  with  Tank  Washers. 
Aggregates:  Broken  Stone — Gravel — Slag  and  Cinders — Balanced  Ag- 
gregate—Size of  Aggregate— Cost  of  Aggregate— Screened  and  Crusher 
Run  Stone  for  Concrete — Quarrying  and  Crushing  Stone — Screening  and 
Washing  Gravel. 

CHAPTER  II.— THEORY  AND  PRACTICE  OF   PROPORTIONING  CON- 
CRETE       25 

Voids:  Voids  in  Sand;  Effect  of  Mixture— Effect  of  Size  of  Grains- 
Voids  in  Broken  Stone  and  Gravel;  Effect  of  Method  of  Loading; 
Test  Determinations;  Specific  Gravity;  Effect  of  Hauling — Theory  of 
the  Quantity  of  Cement  in  Mortar;  Tables  of  Quantities  in  Mortar — 
Tables  of  Quantities  in  Concrete — Percentage  of  Water  in  Concrete — 
Methods  of  Measuring  and  Weighing;  Automatic  Measuring  Devices. 
CHAPTER  III.— METHODS  AND  COSTS  OF  MAKING  AND  PLACING 

CONCRETE   BY  HAND 45 

Loading    into    Stock   Piles — Loading   from    Stock    Piles — Transporting 
Materials  to  Mixing  Boards — Mixing — Loading  and  Hauling  Mixed  Con- 
crete— Dumping,    Spreading  and    Ramming — Cost  of   Superintendence — 
Summary  of  Costs. 
CHAPTER    IV.— METHODS    AND    COST    OF    MAKING    AND    PLACING 

CONCRETE   BY  MACHINE Cl 

Introduction — Conveying  and  Hoisting  Devices — Unloading  with  Grab 
Buckets — Inclines — Trestle  and  Car  Plants — Cableways — Belt  Con- 
veyors— Chutes — Methods  of  Charging  Mixers — Charging  by  Gravity 
from  Overhead  Bins;  Charging  with  Wheelbarrows;  Charging  with 
Cars;  Charging  by  Shoveling;  Charging  with  Derricks — Types  of  Mix- 
ers: Batch  Mixers;  Chicago  Improved  Cube  Tilting  Mixer,  Ransome 
Non-Tilting  Mixer,  Smith  Tilting  Mixer;  Continuous  Mixers;  Eureka 
Automatic  Feed  Mixer;  Gravity  Mixers;  Gilbreth  Trough  Mixer,  Hains 
Gravity  Mixer — Output  of  Mixers — Mixer  Efficiency. 
CHAPTER  V.— METHODS  AND  COST  OF  DEPOSITING  CONCRETE 

UNDER  WATER  AND  OF  SUBAQUEOUS  GROUTING 86 

Introduction — Depositing  in  Closed  Buckets;  O'Rourke  Bucket;  Cy- 
clopean Bucket;  Steubner  Bucket — Depositing  in  Bags — Depositing 
Through  a  Tremie;  Charlestown  Bridge;  Arch  Bridge  Piers,  France; 
Nussdorf  Lock,  Vienna — Grouting  Submerged  Stone;  Tests  of  H.  F. 
White;  Hermitage  Breakwater. 

CHAPTER  VI.— METHODS  AND  COST  OF  MAKING  AND  USING  RUB- 
BLE AND  ASPHALTIC   CONCRETE 98 

Introduction — Rubble  Concrete:  Chattahoochee  River  Dam;  Barossa 
Dam,  South  Australia;  other  Rubble  Concrete  Dams,  Boonton  Dam, 
Spier  Falls  Dam,  Hemet  Dam,  Small  Reservoir  Dam,  Boyd's  Corner 
Dam;  Abutment  for  Railway  Bridge;  English  Data,  Tharsis  &  Calamas 
Ry.,  Bridge  Piers,  Nova  Scotia— Asphalt  Concrete;  Slope  Paving  for 
Earth  Dam;  Base  for  Mill  Floor. 
CHAPTER  VII.— METHODS  AND  COST  OF  LAYING  CONCRETE  IN 

FREEZING  WEATHER   112 

Introduction— Lowering   the    Freezing    Point    of    the    Mixing    Water; 


vj  CONTEXTS. 

Common  Salt  (Sodium  Chloride) :—  Freezing  Temperature  Chart— Heat- 
ing Concrete.  Materials;  Portable  Heaters;  Heating  in  Stationary  Bins; 
Other  Examples  of  Heating  Methods,  Power  Plant,  Billings,  Mont., 
Wachusett  Dam,  Huronian  Power  Co.  Dam,  Arch  Bridge,  Piano,  111., 
Chicago,  Burlington  &  Quincy  R.  R.  Work,  Heating  in  Water  Tank- 
Covering  and  Housing  the  Work;  Method  of  Housing  in  Dam,  Chau- 
diere  Falls,  Quebec;  Method  of  Housing  in  Building  Work. 
CHAPTER  VIII.— METHODS  AND  COST  OF  FINISHING  CONCRETE 

SURFACES 12-» 

Imperfectly  Made  Forms — Imperfect  Mixing  and  Placing — Efflores- 
cence— Spaded  and  Troweled  Finishes — Plaster  and  Stucco  Finish — 
Mortar  and  Cement  Facing — Special  Facing  Mixtures  for  Minimizing 
Form  Marks— Washes— Finishing  by  Scrubbing  and  Washing- 
Finishing  by  Etching  with  Acid— Tooling  Concrete  Surfaces— Gravel  or 
Pebble  Surface  Finish — Colored  Facing. 

CHAPTER  IX.— METHODS  AND  COST  OF  FORM  CONSTRUCTION 136 

Introduction — Effect  of  Design  on  Form  Work — Kind  of  Lumber — 
Finish  and  Dimensions  of  Lumber — Computation  of  Forms — Design  and 
Construction — Unit  Construction  of  Forms — Lubrication  of  Forms — 
Falsework  and  Bracing— Time  for  and  Method  of  Removing  Forms- 
Estimating  and  Cost  of  Form  Work. 
•  'IIAPTER  X.— METHODS  AND  COST  OF  CONCRETE  PILE  AND  PIER 

CONSTRUCTION  151 

Introduction — Molding   Piles  in  Place;   Method  of   Constructing   Ray- 
mond  Piles;    Method  of  Constructing    Simplex   Piles;   Method   of  Con- 
structing Piles  with  Enlarged  Footings;  Method   of  Constructing  Piles 
by  the  Compressol  System;   Method  of  Constructing  Piers  in  Caissons 
—Molding   Piles   for  Driving— Driving  Molded   Piles:    Method  and  Cost 
of  Molding  and  Jetting  Piles   for  an   Ocean   Pier;   Method   of  Molding 
and  Jetting  Square  Piles  for  a  Building  Foundation;  Method  of  Molding 
and    Jetting   Corrugated   Piles    for  a   Building   Foundation;    Method    of 
,     Molding  and  Driving  Round   Piles;   Molding  and   Driving   Square   Piles 
for  a  Building  Foundation;  Method  of  Molding  and  Driving  Octagonal 
Piles — Method  and  Cost  of  Making  Reinforced  Piles  by  Rolling. 
CHAPTER  XI.— METHODS  AND  COST  OF  HEAVY  CONCRETE  WORK 
IN    FORTIFICATIONS,    LOCKS,    DAMS,    BREAKWATERS    AND 

PIERS 184 

Introduction— Fortification  Work:  Gun  Emplacement,  Staten  Island, 
N.  Y.,  Mortar  Battery  Platform,  Tampa  Bay,  Fla.,  Emplacement  for 
Battery,  Tampa  Bay,  Fla.;  U.  S.  Fortification  Work — Lock  Walls, 
Cascades  Canal — Locks,  Coosa  River,  Alabama — Lock  Walls,  Illinois 
&  Mississippi  Canal — Hand  Mixing  and  Placing  Canal  Lock  Founda- 
tions— Breakwater  at  Marquette,  Mich. — Breakwater,  Buffalo,  N.  Y. — 
Breakwater,  Port  Colborne,  Ontario — Concrete  Block  Pier,  Superior 
Entry,  Wisconsin— Dam,  Richmond,  Ind.— Dam  at  McCall  Ferry,  Pa.— 
Dam  at  Chaudiere  Falls,  Quebec. 
CHAPTER  XII.— METHODS  AND  COST  OF  CONSTRUCTING  BRIDGE 

PIERS    AND   ABUTMENTS 230 

Introduction— Rectangular  Pier  for  a  Railway  Bridge— Backing  for 
Bridge  Piers  and  Abutments — Pneumatic  Caissons,  Williamsburg  Bridge 
—Filling  Pier  Cylinders— Piers,  Calf  Killer  River  Bridge— Constructing 
21  Bridge  Piers— Permanent  Way  Structures,  Kansas  City  Outer  Belt 
&  Electric  Ry.— Plate  Girder  Bridge  Abutments— Abutments  and  Piers, 
Lonesome  Valley  Viaduct— Hand  Mixing  and  Wheelbarrow  Work  for 
Bridge  Piers. 

CHAPTER  XIII.— METHODS  AND  COST  OF  CONSTRUCTING  RETAIN- 
ING  WALLS    j ;  259 

Introduction— Comparative  Economy  of  Plain  and  Reinforced  Concrete 
Walls— Form  Construction— Mixing  and  Placing  Concrete— Walls  in 


CONTENTS.  vii 

Trench — Chicago     Drainage     Canal — Grand     Central     Terminal,      New 
York,   N.    Y.— Wall    for   Railway    Yard— Footing    for    Rubble    Stone    Re- 
taining Walls — Track  Elevation,  Allegheny,   Pa.                • 
CHAPTER    XIV.— METHODS    AND    COST    OF    CONSTRUCTING    CON- 
CRETE  FOUNDATIONS  FOR  PAVEMENT 288 

Introduction — Mixtures  Employed — Distribution  of  Stock  Piles — Hints 
on  Hand  Mixing — Methods  of  Machine  Mixing — Foundation  for  Stone 
Block  Pavement,  New  York,  N.  Y. — Foundation  for  Pavement.  New 
Orleans,  La. — Foundation  for  Pavement,  Toronto,  Canada — Miscellan- 
eous Examples  of  Pavement  Foundation  Work — Foundation  for  Brick 
Pavement,  Champaign,  111. — Foundation  Construction  using  Continuous 
Mixers. — Foundation  Construction  for  Street  Railway  Track  Using 
Continuous  Mixers — Foundation  Construction  Using  Batch  Mixers  and 
Wagon  Haulage — Foundation  Construction  Using  a  Traction  Mixer — 
Foundation  Construction  Using  a  Continuous  Mixer — Foundation  Con- 
struction Using  a  Portable  Batch  Mixer. 

CHAPTER    XV.— METHODS    AND    COST    OF    CONSTRUCTING    SIDE- 
WALKS, PAVEMENTS,  AND  CURB  AND  GUTTER 307 

Introduction — Cement  Sidewalks:  General  Method  of  Construction — 
Bonding  of  Wearing  Surface  and  Base — Protection  of  Work  from  Sun 
and  Frost — Cause  and  Prevention  of  Cracks — Cost  of  Cement  Walks; 
Toronto,  Ont. ;  Quincy,  Mass.;  San  Francisco,  Cal.;  Cost  in  Iowa. 
Concrete  Pavement:  Windsor,  Ontario — Richmond,  Ind.  Concrete  Curb 
and  Gutter:  Form  Construction — Concrete  Mixtures  and  Concreting — 
Cost  of  Curb  and  Gutter;  Ottawa,  Canada;  Champaign,  111. 
CHAPTER  XVI.— METHODS  AND  COST  OF  LINING  TUNNELS  AND 

SUBWAYS 328 

Introduction— Capitol  Hill  Tunnel,  Pennsylvania  R.  R.,  Washington, 
D.  C.— Constructing  Side  Walls  in  Relining  Mullan  Tunnel— Lining  a 
Short  Tunnel,  Peekskill,  N.  Y. — Cascade  Tunnel  Great  Northern  Ry. — 
Relining  Hodges  Pass  Tunnel,  Oregon  Short  Line  Ry.— Lining  a  4,000- 
ft.  Tunnel— Method  of  Mixing  and  Placing  Concrete  for  a  Tunnel 
Lining— Gunnison  Tunnel— New  York  Rapid  Transit  Subway— Traveling 
Forms  for  Lining  New  York  Rapid  Transit  Railway  Tunnels— Subway 
Lining,  Long  Island  R.  R.,  Brooklyn,  N.  Y. 
CHAPTER  XVII.— METHODS  AND  COST  OF  CONSTRUCTING  ARCH 

AND    GIRDER    BRIDGES 303 

Introduction— Centers— Mixing  and  Transporting  Concrete;  Cableway 
Plants;  Car  Plant  for  4-Span  Arch  Bridge;  Hoist  and  Car  Plant  for 
21-Span  Arch  Viaduct;  Traveling  Derrick  Plant  for  4-Span  Arch  Bridge 
— Concrete  Highway  Bridges  Green  County,  Iowa — Highway  Girder 
Bridges— Molding  Slabs  for  Girder  Bridges— Connecticut  Ave.  Bridge, 
Washington,  D.  C  — Arch  Bridges,  Elkhart,  Ind.— Arch  Bridge,  Plain - 
well,  Mich.— Five  Span  Arch  Bridge — Arch  Bridge,  Grand  Rapids, 
Mich. 

.CHAPTER  XVIII.— METHODS  AND   COST   OF  CULVERT   CONSTRUC- 
TION     -*14 

Introduction — Box  Culvert  Construction,  C,  B.  &  Q.  R.  R. — 
Arch  Culvert  Costs,  N.  C.  &  St.  L.  Ry. ;  18-ft.  Arch  Culvert;  Six  Arch 
Culverts  6  to  16-ft.  Span;  14%-ft.  Arch  Culvert— Culverts  for  New  Con- 
struction, Wabash  Ry.— Small  Arch  Culvert  Costs,  Pennsylvania  R.  R.— 
26-ft.  Span  Arch  Culvert— 12-ft.  Culvert, '  Kalamazoo,  Mich.— Method 
and  Cost  of  Molding  Culvert  Pipe. 
CHAPTER  XIX.— METHODS  AND  COST  OF  REINFORCED  CONCRETE 

BUILDING   CONSTRUCTION    43S 

Introduction— Construction,  Erection  and  Removal  of  Forms:  Column 
Forms;  Rectangular  Columns;  Polygonal  Columns;  Circular  Columns; 
Ornamental  Columns— Slab  and  Girder  Forms;  Slab  and  I-Beam  Floors; 
Concrete  Slab  and  Girder  Floors— Wall  Forms— Erecting  Forms— Re- 
moving Forms.  Fabrication  and  Placing  Reinforcement:  Fabrication: 


viii  CONTENTS. 

Placing— Mixing,  Transporting  and  Placing  Concrete:  Mixing;  Trans- 
porting; Bucket  Hoists;  Platform  Hoists;  Derricks— Placing  and  Ram- 
ming—ConstrucHng  Wall  Columns  for  a  Brick  Building— Floor  and  Col- 
umn Construction  for  a  Six-Story  Building— Wall  and  Roof  Construc- 
tion for  One-Story  Car  Barn — Constructing  Wall  Columns  for  a  One- 
Story  Machine  Shop— Constructing  One-Story  Walls  with  Movable 
Forms  and  Gallows  Frames— Floor  and  Roof  Construction  for  Four- 
Story  Garage. 

CHAPTER  XX.— METHOD  AND  COST  OF  BUILDING  CONSTRUCTION 

OF   SEPARATELY  MOLDED   MEMBERS 515 

Introduction— Column,  Girder  and  Slab  Construction:  Warehouses, 
Brooklyn,  N.  Y.;  Factory,  Reading,  Pa.;  Kilnhouse,  New  Village,  N.  J. 
— Hollow  Block  Wall  Construction:  Factory  Buildings,  Grand  Rapids, 
Mich.;  Residence,  Quogue,  N.  Y.,  Two- Story  Building,  Albuquerque, 
N.  Mex.;  General  Cost  Data. 

CHAPTER  XXI.— METHODS  AND  COST  OF  AQUEDUCT  AND  SEWER 

CONSTRUCTION  ' 532 

Introduction — Forms  and  Centers — Concreting — Reinforced  Conduit, 
Salt  River  Irrigation  Works,  Arizona— Conduit,  Torresdale  Filters, 
Philadelphia,  Pa.— Conduit,  Jersey  City  Water  Supply,  Twin  Tube 
Water  Conduit  at  Newark,  N.  J. — 66-in.  Circular  Sewer,  South  Bend, 
Ind. — Sewer  Invert  Haverhill,  Mass. — 29-ft.  Sewer,  St.  Louis,  Mo. — 
Sewer,  Middlesborough,  Ky. — Intercepting  Sewer,  Cleveland,  Ohio — 
Reinforced  Concrete  Sewer,  Wilmington,  Del. — Sewer  with  Monolithic 
Invert  and  Block  Arch — Cost  of  Block  Manholes — Cement  Pipe  Con- 
structed in  Place — Pipe  Sewer,  St.  Joseph,  Mo. — Cost  of  Molding  Small 
Cement  Pipe — Molded  Pipe  Water  Main,  Swansea,  England. 

CHAPTER   XXII.— METHODS    AND    COST    OF    CONSTRUCTING    RES- 
ERVOIRS   AND    TANKS 588 

Introduction — Small  Covered  Reservoir — 500,000  Gallon  Covered  Reser- 
voir, Ft.  Meade,  So.  Dak. — Circular  Reservoir,  Bloomington,  111. — Stand- 
pipe  at  Attleborough,  Mass. — Gas  Holder  Tank,  Des  Moines,  Iowa — Gas 
Holder  Tank,  New  York  City — Lining  a  Reservoir,  Quincy,  Mass. — Re- 
lining  a  Reservoir,  Chelsea,  Mass. — Lining  Jerome  Park  Reservoir — 
Reservoir  Floor,  Canton,  111.— Reservoir  Floor,  Pittsburg,  Pa.— Con- 
structing a  Silo— Groined  Arch  Reservoir  Roof— Grain  Elevator  Bins. 

CHAPTER  XXIII.— METHODS  AND  COST  OF  CONSTRUCTING  ORNA- 
MENTAL  WORK 636 

Introduction — Separately  Molded  Ornaments:  Wooden  Molds;  Iron 
Molds;  Sand  Molding;  Plaster  Molds — Ornaments  Molded  in  Place: 
Big  Muddy  Bridge;  Forest  Park  Bridge;  Miscellaneous  Structures. 

CHAPTER  XXIV.— MISCELLANEOUS  METHODS  AND  COSTS 653 

Introduction — Drilling  and  Blasting  Concrete — Bench  Monuments, 
Chicago,  111. — Pole  Base — Mile  Post — Bonding  New  Concrete  to  Old — 
Dimensions  and  Capacities  of  Mixers — Data  for  Estimating  Weight  of 
Steel  in  Reinforced  Concrete;  Computing  Weight  from  Percentage  of 
Volume;  Weights  and  Dimensions  of  Plain  and  Special  Reinforcing 
Metals — Recipes  for  Coloring  Mortars. 

CHAPTER  XXV.— METHODS  AND  COST  OF  WATERPROOFING  CON- 
CRETE   STRUCTURES    667 

Impervious  Concrete  Mixtures — Star  Stetten  Cement — Medusa  Water- 
proofing Compound — Novoid  Waterproofing  Compound — Impermeable 
Coatings  and  Washes:  Bituminous  Coatings;  Szerelmey  Stone  Liquid 
Wash;  Sylvester  Wash;  Sylvester  Mortars;  Hydrolithic  Coating;  Ce- 
ment Mortar  Coatings:  Oil  and  Parafflne  Washes— Impermeable  Dia- 
phragms; Long  Island  R.  R.  Subway;  New  York  Rapid  Transit 
Subway. 


^     THE 

^ERSITY 


Concrete    Construction 
Methods    and   Cost 


CHAPTER  I. 

.METHODS    AND    COST    OF    SELECTING   AND    PRE- 
PARING MATERIALS  FOR  CONCRETE. 

Concrete  is  an  artificial  stone  produced  by  mixing  cement 
mortar  with  broken  stone,  gravel,  broken  slag,  cinders  or 
other  similar  fragmentary  materials.  The  component  parts 
are  therefore  hydraulic  cement,  sand  and  the  broken  stone  or 
other  coarse  material  commonly  designated  as  the  aggregate. 

CEMENT. 

At  least  a  score  of  varieties  of  hydraulic  cement  are  listed 
in  the  classifications  of  cement  technologists.  The  construct- 
ing engineer  and  contractor  recognize  only  three  varieties : 
Portland  cement,  natural  cement  and  slag  or  puzzolan  cement. 
All  concrete  used  in  engineering  work  is  made  of  either  Port- 
land, natural  or  slag  cement,  and  the  great  bulk  of  all  concrete 
is  made  of  Portland  cement.  Only  these  three  varieties  of 
cement  are,  therefore,  considered  here  and  they  only  in  their 
aspects  having  relation  to  the  economics  of  construction  work. 
For  a  full  discussion  of  the  chemical  and  physical  properties 
of  hydraulic  cements  and  for  the  methods  of  determining 
these  properties  by  tests,  the  reader  is  referred  to  "Practical 
Cement  Testing,"  by  W.  Purves  Taylor. 

PORTLAND  CEMENT.— Portland  cement  is  the  best  of 
the  hydraulic  cements.  Being  made  from  a  rigidly  controlled 
artificial  mixture  of  lime,  silica  and  alumina  the  product  of 
the  best  mills  is  a  remarkably  strong,  uniform  and  stable 
material.  It  is  suitable  for  all  classes  of  concrete  work  and 
is  the  only  variety  of  hydraulic  cement  allowable  for  rein- 
forced concrete  or  for  plain  concrete  having  to  endure  hard 


2  CONCRETE    CONSTRUCTION. 

wear  or  to  be  used  where  strength,  density  and  durability  of 
high  degree  are  demanded. 

NATURAL  CEMENT.— Natural  cement  differs  from  Port- 
land cement  in  degree  only.  It  is  made  by  calcining  and 
grinding  a  limestone  rock  containing  naturally  enough  clayey 
matter  (silica  and  alumina)  to  make  a  cement  that  will  harden 
under  water.  Owing  to  the  imperfection  and  irregularity  of 
the  natural  rock  mixture,  natural. cement  is  weaker  and  less 
uniform  than  Portland  cement.  Natural  cement  concrete,  is 
suitable  for  work  in  which  great  unit  strength  or  uniformity 
of  quality  is  not  essential.  It  is  never  used  for  reinforced 
work. 

SLAG  CEMENT. — Slag  cement  has  a  strength  approach- 
ing very  closely  that  of  Portland  cement,  but  as  it  will  not 
stand  exposure  to  the  air  slag  cement  concrete  is  suitable  for 
use  only  under  water.  Slag  cement  is  made  by  grinding 
together  slaked  lime  and  granulated  blast  furnace  slag. 

SIZE  AND  WEIGHT  OF  BARRELS  OF  CEMENT.— 
The  commercial  unit  of  measurement  of  cement  is  the  barrel ; 
the  unit  of  shipment  is  the  bag.  A  barrel  of  Portland  cement 
contains  380  Ibs.  of  cement,  and  the  barrel  itself  weighs  20  Ibs. ; 
there  are  four  bags  (cloth  or  paper  sacks)  of  cement  to  the 
barrel,  and  the  regulation  cloth  sack  weighs  il/2  Ibs.  The 
size  of  cement  barrels  varies,  due  to  the  differences  in  weight 
of  cement  and  to  differences  in  compacting  the  cement  into 
the  barrel.  A  light  burned  Portland  cement  weighs  100  Ibs. 
per  struck  bushel;  a  heavy  burned  Portland  cement  weighs 
118  to  125  Ibs.  per  struck  bushel.  The  number  of  cubic  feet 
of  packed  Portland  cement  in  a  barrel  ranges  from  3  to  3^2. 
Natural  cements  are  lighter  than  Portland  cement.  A  barrel 
of  Louisville,  Akron,  Utica  or  other  Western  natural  cement 
contains  265  Ibs.  of  cement  and  weighs  15  Ibs.  itself;  a  barrel 
of  Rosendale  or  other  Eastern  cement  contains  300  Ibs.  of 
cement  and  the  barrel  itself  weighs  20  Ibs.  There  are  3%  cu. 
ft.  in  a  barrel  of  Louisville  cement.  Usually  there  are  three 
bags  to  a  barrel  of  natural  cement. 

As  stated  above,  the  usual  shipping  unit  for  cement  is  the 
bag,  but  cement  is  often  bought  in  barrels  or,  for  large  works, 
in  bulk.  When  bought  in  clotli  bags,  a  charge  is  made  of 


MATERIALS    FOR    CONCRETE.  ^ 

10  cts.  each  for  the  bags,  but  on  return  of  the  bags  a  credit  of 
8  to  10  cts.  each  is  allowed.  Cement  bought  in  barrels  costs 
10  cts.  more  per  barrel  than  in  bulk,  and  cement  ordered  in 
paper  bags  costs  5  cts.  more  per  barrel  than  in  bulk.  Cement 
is  usually  bought  in  cloth  sacks  which  are  returned,  but  to  get 
the  advantage  of  this  method  of  purchase  the  user  must  have 
an  accurate  system  for  preserving,  checking  up  and  shipping 
the  bags. 

Where  any  considerable  amount  of  cement  is  to  be  used  the 
contractor  will  find  that  it  will  pay  to  erect  a  small  bag  house 
or  to  close  off  a  room  at  the  mixing  plant.  Provide  the  en- 
closure with  a  locked  door  and  with  a  small  window  into 
which  the  bags  are  required  to  be, thrown  as  fast  as  emptied. 
One  trustworthy  man  is  given  the  key  and  the  task  of  count- 
ing up  the  empty  bags  each  day  to  see  that  they  check  with 
the  bags  of  cement  used.  The  following  rule  for  packing 
and  shipping  is  given  by  Gilbreth.* 

"Pack  cement  bags  laid  flat,  one  on  top  of  the  other,  in 
piles  of  50.  They  can  then  be  counted  easily.  Freight  must 
be  prepaid  when  cement  bags  are  returned  and  bills  of  lading 
must  be  obtained  in  duplicate  or  credit  cannot  be  obtained 
on  shipment/' 

The  volumes  given  above  are  for  cement  compacted  in  the 
barrel.  When  the  cement  is  emptied  and  shoveled  into  boxes 
it  measures  from  20  to  30  per  cent  more  than  when  packed 
in  the  barrel.  The  following  table  compiled  from  tests  made 
for  the  Boston  Transit  Commission,  Mr.  Howard  Carson, 
Chief  Engineer,  in  1896,  shows  the  variation  in  volume  of 
cement  measured  loose  and  packed  in  barrels : 

Per  cent 

Brand  Vol.  Barrel  Vol.  Packed    Vol.  Loose  Increase 

Portland.  cu.  ft.  cu.  ft.  cu.  ft.  in  bulk 

Giant 3.5  3.35  4^7  25 

Atlas   3.45  3-21  375  l8 

Saviors   3.25  3.15  4-O5  3° 

Alsen 3.22  3.16  4.19  33 

Dyckerhoff  ..  .  .    3.12  3.03  4-°o  33 

Mr.  Clarence  M.  Foster  is  authority  for  the  statement  that 


""Field    System,"    Frank    B.    Gilbreth.      Myron   C.    Clark  Publishing:  Co., 
New  York  and   Chicago. 


CONCRETE    CONSTRUCTION. 


Utica  cement  barrels  measure  i61/^  ins.  across  at  the  heads, 
1^/2  ins.  across  the  bilge,  and  2^/4  ins.  in  length  under  heads, 
and  contain  3.77  cu.  ft.  When  265  Ibs.  of  Utica  natural  hy- 
draulic cement  are  packed  in  a  barrel  it  fills  it  within  2l/2  ins. 
of  the  top  and  occupies  3.45  cu.  ft.,  and  this  is  therefore  the 
volume  of  a  barrel  of  Utica  hydraulic  cement  packed  tight. 

In  comparative  tests  made  of  the  weights  and  volumes  of 
various  brands  of  cements  at  Chicago  in  1903,  the  following 
figures  were  secured  : 

Vol.  per  Weight  per  Weight  per 

bbl.,  cu.  ft.  bbl.,  Ibs.  cu.  ft 

Brand.              Loose.  Gross.             Net.  Loose,  Ibs. 

Dyckerhoff  ...  447  395               369-5  83 

Atlas    ........  445  401               3Sl  85-5 

Alpha   ........  4.37  400.5             381  86.5 

Puzzolan   .....  4-84  375               353-5  73-5 

Steel    .........  4.96  345                322.5  67.5 

Hilton    .....  ..4.64  393               370.5  79.5 

SPECIFICATIONS  AND  TESTING—  The  great  bulk  of 
cement  used  in  construction  work  is  bought  on  specification. 
The  various  government  bureaus,  state  and  city  works  de- 
partments, railway  companies,  and  most  public  service  cor- 
porations have  their  own  specifications.  Standard  specifica- 
tions are  also  put  forward  by  several  of  the  national  engineer- 
ing societies,  and  one  of  these  or  the  personal  specification  of 
the  engineer  is  used  for  individual  works.  Buying  cement  to 
specification  necessitates  testing  to  determine  that  the  mate- 
rial purchased  meets  the  specified  requirements.  For  a  com- 
plete discussion  of  the  methods  of  conducting  such  tests  the 
reader  is  referred  to  "Practical  Cement  Testing"  by  W.  Purves 
Taylor. 

According  to  this  authority  a  field  testing  laboratory  will 
cost  for  equipment  $250  to  $350.  Such  a  laboratory  can  be 
operated  by  two  or  three  men  at  a  salary  charge  of  from  $100 
to  $200  per  month.  Two  men  will  test  on  an  average  four 
samples  per  day  and  each  additional  man  will  test  four  more 
samples.  The  cost  of  testing  will  range  from  $3  to  $5  per 
sample,  which  is  roughly  equivalent  to  3  cts.  per  barrel  of 


MATERIALS    FOR    CONCRETE.  5 

cement,  or  from  3  to  5  cts.  per  cubic  yard  of  concrete.  These 
figures  are  for  field  laboratory  work  reasonably  well  con- 
ducted under  ordinarily  favorable  conditions.  In  large  labor- 
atories the  cost  per  sample  will  run  somewhat  lower. 

SAND. 

Sand  constitutes  from  ^  to  ^  of  the  volume  of  concrete ; 
when  a  large  amount  of  concrete  is  to  be  made  a  contractor 
cannot,  therefore,  afford  to  guess  at  his  source  of  sand  supply. 
A  long  haul  over  poor  roads  can  easily  make  the  sand  cost 
more  than  the  stone  per  cubic  yard  of  concrete. 

PROPERTIES  OF  GOOD  SAND.— Engineers  commonly 
specify  that  sand  for  concrete  shall  be  clean  and  sharp,  and 
silicious  in  character.  Neither  sharpness  nor  excessive  clean- 
liness is  worth  seeking-  after  if  it  involves  much  expense. 
Tests  show  conclusively  that  sand  with  rounded  grains  makes 
quite  as  strong  a  mortar,  other  things  being  equal,  as  does 
sand  with  angular  grains.  The  admixture  with  sand  of  a  con- 
siderable percentage  of  loam  or  clay  is  also  not  the  unmixed 
evil  it  has  been  supposed  to  be.  Myron  S.  Falk  records*  a 
number  of  elaborate  experiments  on  this  point.  These  ex- 
periments demonstrate  conclusively  that  loam  and  clay  in 
sand  to  the  amount  of  10  to  15  per  cent,  result  in  no  material 
reduction  in  the  strength  of  mortars  made  with  this  sand  as 
compared  with  mortars  made  with  the  same  sand  after  wash- 
ing. There  can  be  no  doubt  but  that  for  much  concrete  work 
the  expense  entailed  in  washing  sand  is  an  unnecessary  one. 

The  only  substitute  for  natural  sand  for  concrete,  that  need 
be  considered  practically,  is  pulverized  stone,  either  the  dust 
'  and  fine  screenings  produced  in  crushing  rock  or  an  artificial 
sand  made  by  reducing  suitable  rocks  to  powder.  As  a  con- 
clusion from  the  records  of  numerous  tests,  M.  S.  Falk  says: 
"It  may  be  concluded  that  rock  screenings  may  be  substituted 
for  sand,  either  in  mortar  or  concrete,  without  any  loss  of 
strength  resulting.  This  is  important  commercially,  for  it 
precludes  the  necessity  of  screening  the  dust  from  crushed 
rock  and  avoids,  at  the  same  time,  the  cost  of  procuring  a 
natural  sand  to  take  its  place." 

*"Cements,  Mortars  ami  Concretes  "     By  Myron  S.  Falk.     Myron  C.  Clark 
Publishing   Co.,    Chicago,   111. 


6  CONCRETE    CONSTRUCTION. 

The  principal  danger  in  using  stone  dust  is  failure  to  secure 
the  proper  balance  of  different  size  grains.  This  is  also  an 
important  matter  in  the  choice  of  natural  sands.  Sand  com- 
posed of  a  mixture  of  grains  ranging  from  fine  to  coarse  gives 
uniformly  stronger  mortars  than  does  sand  with  grains  of 
nearly  one  size,  and  as  between  a  coarse  and  a  fine  sand  of 
one  size  of  grains  the  coarse  sand  gives  the  stronger  mortar. 
Further  data  on  the  effect  of  size  of  grains  on  the  utility  of 
sand  for  concrete  are  given  in  Chapter  II,  in  the  section  on 
Voids  in  Sand,  and  for  those  who  wish  to  study  in  detail,  the 
test  data  on  this  and  the  other  matters  referred  to  here,  the 
authors  recommend  "Cements,  Mortars  and  Concretes ;  Their 
Physical  Properties,"  by  Myron  S.  Falk. 

COST  OF  SAND. — A  very  common  price  for  sand  in  cities 
is  $i  per  cu.  yd.,  delivered  at  the  work.  It  may  be  noted  here 
that  as  sand  is  often  sold  by  the  load  instead  of  the  cubic  yard, 
it  is  wise  to  have  a  written  agreement  defining  the  size  of  a 
load.  Where  the  contractor  gets  his  sand  from  the  pit  its  cost 
will  be  the  cost  of  excavating  and  loading  at  the  pit,  the  cost 
of  hauling  in  wagons,  the  cost  of  freight  and  rehandling  it  if 
necessary,  and  the  cost  of  washing,  added  together. 

An  energetic  man  working  under  a  good  foreman  will  lo#d 
20  cu.  yds.  of  sand  into  wagons  per  lo-hour  day ;  with  a  poor 
foreman  or  when  laborers  are  scarce,  it  is  not  safe  to  count 
on  more  than  15  cu.  yds.  per  day.  With  wages  at  $1.50  per 
day  this  will  make  the  cost  of  loading  10  cts.  per  cubic  yard. 
The  cost  of  hauling  will  include  the  cost  of  lost  team  time  and 
dumping,  which  will  average  about  5  cts.  per  cubic  yard. 
With  i  cu.  yd.  loads,  wages  of  team  35  cts.  per  hour,  and 
speed  of  travel  2^2  miles  per  hour,  the  cost  of  hauling  proper 
is  l/2  ct.  per  100  ft.,  or  27  cts.  per  mile.  Assuming  a  mile  haul, 
the  cost  of  sand  delivered  based  on  the  above  figures  will  be 
10  cts.  -j-  5  cts.  -f  y2  ct.  per  100  ft.  =  15+27  cts.  =  42  cts.  per 
cu.  yd.  Freight  rates  can  always  be  secured  and  it  is  usually 
safe  to  estimate  the  weight  on  a  basis  of  2,700  Ibs.  per  cubic 
yard.  For  a  full  discussion  of  the  cost  of  excavating  sand 
and  other  earths  the  reader  is  referred  to  "Earth  Excavation 
•and  Embankments;  Methods  and  Cost,"  by  Halbert  P.  Gil- 
lette and  Daniel  J.  Hauer. 


MATERIALS    FOR    CONCRETE.  7 

METHODS  AND  COST  OF  WASHING  SAND.— When 
the  available  sand  carries  considerable  percentages  of  loam  or 
clay  and  the  specifications  require  that  clean  sand  shall  be 
used,  washing  is  necessary.  The  best  and  cheapest  method 
of  performing  this  task  will  depend  upon  the  local  conditions 
and  the  amount  of  sand  to  be  washed. 

Washing  With  Hose. — When  the  quantity  of  sand  to  be 
washed  does  not  exceed  15  to  30  cu.  yds.  per  day  the  simplest 
method,  perhaps,  is  to  use  a  hose.  Build  a  wooden  tank  or 
box,  8  ft.  wide  and  15  ft.  iong,  the  bottom  having  a  slope  of 
8  ins.  in  the  15  ft.  The  sides  should  be  about  8  ins.  high  at 
the  lower  end  and  rise  gradually  to  3  ft.  in  height  at  the  upper 
end.  Close  the  lower  end  of  the  tank  with  a  board  gate  about 
6  ins.  in  height  and  sliding  in  grooves  so  that  it  can  be  re- 
moved. Dump  about  3  cu.  yds.  of  sand  into  the  upper  end  of 
the  tank  and  play  a  24-in.  hose  stream  of  water  on  it,  the  hose 
man  standing  at  the  lower  end  of  the  tank.  The  water  and 
sand  flow  down  the  inclined  bottom  of  the  tank  where  the 
sand  remains  and  the  dirt  flows  over  the  gate  and  off  with  the 
water.  It  takes  about  an  hour  to  wash  a  3-cu.  yd.  batch,  and 
by  building  a  pair  of  tanks  so  that  the  hose  man  can  shift  from 
one  to  the  other,  washing  can  proceed  continuously  and  one 
man  will  wash  30  cu.  yds.  per  lo-hour  day  at  a  cost,  with 
wages  at  $1.50,  of  5  cts.  per  cubic  yard.  The  sand,  of  course, 
has  to  be  shoveled  from  the  tank  and  this  will  cost  about  10 
cts.  per  cubic  yard,  making  15  cts.  per  cubic  yard  for  washing 
and  shoveling,  and  to  this  must  be  added  any  extra  hauling 
and,  if  the  water  is  pumped,  the  cost  of  pumping  which  may 
amount  to  10  cts.  per  cubic  yard  for  coal  and  wages.  Alto- 
gether a  cost  of  from  15  to  30  cts.  per  cubic  yard  may  be  fig- 
ured for  washing  sand  with  a  hose. 

Washing  With  Sand  Ejectors.— When  large  quantities  of 
sand  are  to  be  washed  use  may  be  made  of  the  sand  ejector 
system,  commonly  employed  in  washing  filter  sand  at  large 
water  filtration  plants;  water  under  pressure  is  required.  In 
this  system  the  dirty  sand  is  delivered  into  a  conical  or  pyra- 
midal hopper,  from  the  bottom  of  which  it  is  drawn  by  an 
ejector  and  delivered  mixed  with  water  into  a  second  similar 
hopper ;  here  the  water  and  dirt  overflow  the  top  of  the  hopper, 


g 


CONCRETE    CONSTRUCTION. 


^  u!>  twa.  NI 


Side        Eleva-l-ion 


Front       Elevation       of      Sand  Washers. 

Fig.    1.— Plan   and   Elevation   of   Two-Hopper   Ejector   Sand  Washing  Plant. 

while  the  sand  settles  and  is  again  ejected  into  a  third  hop- 
per or  to  the  stock  pile  or  bins.     The  system  may  consist  of 


s— f^r^g 


C I  • v  a  T I  on 
Fig.   2.— Plan  and   Elevation  of  Four-Hopper  Ejector  Sand   Washing   Plant. 

anywhere  from  two  to  six  hoppers.     Figure  i  shows  a  two- 
hopper  lay-out  and  Fig.  2  shows  a  four-hopper  lay-out.     In 


MATERIALS    FOR    CONCRETE.  9 

the  first  plant  the  washed  sand  is  delivered  into  bins  so  ar- 
ranged, as  will  be  seen,  that  the  bins  are  virtually  a  third 
washing  hopper.  The  clean  sand  is  chuted  from  these  bins 
directly  into  cars  or  wagons.  In  the  second  plant  the  clean 
sand  is  ejected  into  a  trough  which  leads  it  into  buckets  han- 
dled by  a  derrick.  The  details  of  one  of  the  washing  hoppers 
for  the  plant  shown  by  Fig.  i  are  illustrated  by  Fig.  3. 

At  filter  plants  the  dirty  sand  is  delivered  mixed  with  water 
to  the  first  hopper  by  means  of  ejectors  stationed  in  the  filters 
and  discharging  through  pipes  to  the  washers.  When,  as 
would  usually  be  the  case  in  .contract  work,  the  sand  is  de- 
livered comparatively  dry  to  the  first  hopper,  this  hopper  must 


Vertical    Section    A-B. 

Fig.  3.— Details  of  Washing  Hopper  and  Kjector  for  Plant  Shown  by  Fig.  1. 

1>e  provided  with  a  sprinkler  pipe  to  wet  the  sand.  In  study- 
ing the  ejector  washing  plants  illustrated  it  should  be  borne 
in  mind  that  for  concrete  work  they  would  not  need  to  be  of 
such  permanent  construction  as  for  filter  plants,  the  washers 
would  be  mounted  on  timber  frames,  underground  piping 
would  be  done  away  with,  etc. ;  at  best,  however,  such  plants 
are  expensive  and  will  be  warranted  only  when  the  amount 
of  sand  to  be  washed  is  large. 

The  usual  assumption  of  water-works  engineers  is  that  the 
volume  of  water  required  for  washing  filter  sand  is  15  times 
the  volume  of  the  sand  washed.  At  the  Albany,  N.  Y.,  filters 
the  sand  passes  through  five  ejectors  at  the  rate  of  3  to  5  cu. 


1O 


CONCRETE    CONSTRUCTION. 


yds.  per  hour  and  takes  4,000  gallons  of  water  per  cubic  yard. 

One  man  shovels  sand  into  the  washer  and  two  take  it  away. 

Based  on  an  output   of  32  cu.  yds.  in   10  hours,   Mr.  Allen 

Hazen  estimates  the  cost  of  washing  as  follows : 

3  men,  at  $2  per  day $6.00 

1 10,000  gallons  of  water,  at  $0.05 5.50 

Total,  32  cu.  yds.,  at  36  cts $ii-5° 

Washing  With  Tank  Washers.— Ffgure  4  shows  a  sand 
washer  used  in  constructing  a  concrete  lock  at  Springdale, 
Pa.,  in  the  United  States  government  improvement  work  on 
the  Allegheny  river.  The  device  consisted  of  a  circular  tank 


*&  1 

Fig.  4.— Details  of  Tank  Washer  Used  at  Springdale,  Pa. 

9  ft.  in  diameter  and  7  ft.  high,  provided  with  a  sloping  false 
bottom  perforated  with  i-in.  holes,  through  which  water  was 
forced  as  indicated.  A  jl/2  X  5  X  6-in.  pump  with  a  3-in.  dis- 
charge pipe  was  used  to  force  water  into  the  tank,  and  the 
rotating  paddles  were  operated  by  a  7  h.p.  engine.  This  ap- 
paratus washed  a  batch  of  14  cu.  yds.  in  from  i  to  2  hours  at 
a  cost  of  7  cts.  per  cubic  yard.  The  sand  contained  much  fine 
coal  and  silt.  The  above  data  are  given  by  Mr.  W.  H.  Roper. 
Another  form  of  tank  washer,  designed  by  Mr.  Allen  Hazen, 
for  washing  bank  sand  at  Yonkers,  N.  Y.,  is  shown  by  Fig.  5. 
This  apparatus  consisted  of  a  10  X  2}^  X  2^-ft.  wooden  box, 
with  a  6-in.  pipe  entering  one  end  at  the  bottom  and  there 


MATERIALS    FOR    CONCRETE. 


II 


branching  into  three  3-in.  pipes,  extending  along  the  bottom 
and  capped  at  the  ends.  The  undersides  of  the  3-in.  pipes 
were  pierced  with  y2-m.  holes  6  ins.  apart,  through  which 
water  under  pressure  was  discharged  into  the  box.  Sand  was 


V      I'     *'     3'     V      5.' 

1 .  .    I       I        I        f    .  I 


Waste 
Thwff/y-..  nTS 


Section     A-B. 


Section  C-0. 


Fig.  5.— Details  of  Tank  Washer  Used  at  Yonkers,  N.  Y. 

shoveled  into  the  box  at  one  end  and  the  upward  currents  of 
water  raised  the  fine  and  dirty  particles  until  they  escaped 
through  the  waste  troughs.  When  the  box  became  filled  with 
sand  a  sliding  door  at  one  end  was  opened  and  the  batch  dis- 


ENfc  NEWS 

Fig.   6.—  Details  of  Rotating  Tank  Sand  Washer  Used  at  Hudson,  N.  Y. 

charged.  The  operation  was  continuous  as  long  as  sand  was 
shoveled  into  the  box;  by  manipulating  the  door  the  sand 
could  be  made  to  run  out  with  a  very  small  percentage  of 


12 


CONCRETE    CONSTRUCTION. 


water.  Sand  containing  7  per  cent  of  dirt  was  thus  washed 
so  that  it  contained  only  0.6  per  cent  dirt.  The  washer  han- 
dled 200  cu.  yds.  of  sand  in  10 
hours.  The  above  data  are 
given  by  F.  H.  Stephenson. 

A  somewhat  more  elaborate 
form  of  tank  washer  than 
either  of  those  described  is 
shown  by  Fig.  6.  This  ap- 
paratus was  used  by  Mr.  Geo. 
A.  Soper  for  washing  filter 
sand  at  Hudson,  N.  Y.  The 
dirty  sand  was  shoveled  into  a 
sort  of  hopper,  from  which  it 
was  fed  by  a  hose  stream  into 
an  inclined  cylinder,  along 
which  it  traveled  and  was  dis- 
charged into  a  wooden  trough 
provided  with  a  screw  convey- 
or and  closed  at  both  ends. 
The  water  overflowing  the 
sides  of  the  trough  carried 
away  the  dirt  and  the  clean 
sand  was  delivered  by  the 
screw  to  the  bucket  elevator 
which  hoisted  it  to  a  platform, 
from  which  it  was  taken  by 
barrows  to  the  stock  pile.  A 
4-h.p.  engine  with  a  5-h.p. 
boiler  operated  the  cylinder, 
screw,  elevator  and  pump. 
Four  men  operated  the  washer 
and  handled  32  cu.  yds.  of 
sand  per  day;  with  wages  at 
$1.50  the  cost  of  washing  was 
20  cts.  per  cubic  yard. 

In    constructing   a    concrete 
block  dam  at  Lynchburg,  Va., 

Fig.  7.-Arrangement  of  san(J   containing   from    I  S    to    ^O 

Sand  Washing  Plant  f  J 

at  Lynchburg,  Va.  per    cent,    of    loam,    clay    and 


MATERIALS    FOR    CONCRETE.  13 

vegetable  matter  was  washed  to  a  cleanliness  of  2  to  5  per  cent 
of  such  matter  by  the  device  shown  by  Fig.  7.  A  small  creek 
was  diverted,  as  shown,  into  a  wooden  flume  terminating  in 
two  sand  tanks ;  by  means  of  the  swinging  gate  the  flow  was 
passed  through  either  tank  as  desired.  The  sand  was  hauled 
by  wagon  and  shoveled  into  the  upper  end  of  the  flume ;  the 
current  carried  it  down  into  one  of  the  tanks  washing  the  dirt 
loose  and  carrying  it  off  with  the  overflow  over  the  end  of  the 
tank  while  the  sand  settled  in  the  tank.  When  one  tank  was 
full  the  flow  was  diverted  into  the  other  tank  and  the  sand  in 
the  first  tank  was  shoveled  out,  loaded  into  wagons,  and 
hauled  to  the  stock  pile.  As  built  this  washer  handled  about 
30  cu.  yds.  of  sand  per  lo-hour  day,  but  the  tanks  were  built 
too  small  for  the  flume,  which  could  readily  handle  75  cu.  yds. 
per  day  with  no  larger  working  force.  This  force  consisted 
of  three  men  at  $1.50  per  day,  making  the  cost,  for  a  30  cu.  yd. 
output,  15  cts.  per  cu.  yd.  for  washing. 

None  of  the  figures  given  above  includes  the  cost  of 
handling  the  sand  to  and  from  the  washer.  When  this  in- 
volves much  extra  loading  and  hauling,  it  amounts  to  a  con- 
siderable expense,  and  in  any  plan  for  washing  sand  the  con- 
tractor should  figure,  with  exceeding  care,  the  extra  handling 
due  to  the  necessity  of  washing. 

AGGREGATES. 

The  aggregates  commonly  used  in  making  concrete  are 
broken  or  crushed  stone,  gravel,  slag  and  cinders.  Slag  and 
cinders  make  a  concrete  that  weighs  considerably  less  than 
stone  or  gravel  mixtures,  and  being  the  products  of  com- 
bustion are  commonly  supposed  to  make  a  specially  fire  re- 
sisting concrete ;  their  use  is,  therefore,  confined  very  closely 
to  fire-proof  building  work  and,  in  fact,  to  floor  construction 
for  such  buildings.  Slag  and  cinder  concretes  are  for  this 
reason  given  minor  consideration  in  this  volume. 

BROKEN  STONE. — Stone  produced  by  crushing  any  of 
the  harder  and  tougher  varieties  of  rock  is  suitable  for  con- 
crete. Perhaps  the  best  stone  is  produced  by  crushing  trap 
rock.  Crushed  trap  besides  being  hard  and  tough  is  angu- 
lar and  has  an  excellent  fracture  surface  for  holding  cement ; 
it  also  withstands  heat  better  than  most  stone.  Xext  to 


I4  CONCRETE    CONSTRUCTION. 

trap  the  hard,  tough,  crystalline  limestones  make  perhaps  the 
best  all  around  concrete  material;  cement  adheres  to  lime- 
stone better  than  to  any  other  rock.  Limestone,  however, 
calcines  when  subjected  to  fire  and  is,  therefore,  objected  to 
by  many  engineers  for  building  construction.  The  harder  and 
denser  sandstones,  mica-schists,  granites  and  syanites  make 
good  stone  for  concrete  and  occasionally  shale  and  slate  may 
be  used. 

GRAVEL. — Gravel  makes  one  of  the  best  possible  aggre- 
gates for  concrete.  The  conditions  under  which  gravel  is  pro- 
duced by  nature  make  it  reasonably  certain  that  only  the 
tougher  and  harder  rocks  enter  into  its  composition ;  the 
rounded  shapes  of  the  component  particles  permit  gravel  to 
be  more  closely  tamped  than  broken  stone  and  give  less  danger 
of  voids  from  bridging ;  the  mixture  is  also  generally  a  fairly 
well  balanced  composition  of  fine  and  coarse  particles.  The 
surfaces  of  the  particles  being  generally  smooth  give  per- 
haps a  poorer  bond  with  the  cement  than  most  broken  stone. 
In  the  matter  of  strength  the  most  recent  tests  show  that 
there  is  very  little  choice  between  gravel  and  broken  stone 
concrete. 

SLAG  AND  CINDERS.— The  slag  used  for  concrete  ag- 
gregate is  iron  blast  furnace  slag  crushed  to  proper  size. 
Cinders  for  aggregate  are  steam  boiler  cinders ;  they  are  best 
with  the  fine  ashes  screened  out  and  should  not  contain  more 
than  15  per  cent,  of  unburned  coal. 

BALANCED  AGGREGATE.— With  the  aggregate,  as 
with  the  sand  for  concrete,  the  best  results,  other  things 
being  equal,  will  be  secured  by  using  a  well-balanced  mix- 
ture of  coarse  and  fine  particles.  Usually  the  product  of  a 
rock  crusher  is  fairly  well  balanced  except  for  the  very  fine 
material.  There  is  nearly  always  a  deficiency  of  this,  which, 
as  explained  in  a  succeeding  section,  has  to  be  supplied  by 
adding  sand.  Usually,  also,  the  engineer  accepts  the  crusher 
product  coarser  than  screenings  as  being  well  enough  bal- 
anced for  concrete  work,  but  this  is  not  always  the  case.  En- 
gineers occasionally  demand  an  artificial  mixture  of  varying 
proportions  of  different  size  stones  and  may  even  go  so  far 
as  to  require  gravel  to  be  screened  and  reproportioned.  This 


MATERIALS    FOR    CONCRETE.  15 

artificial  grading  of  the  aggregate  adds  to  the  cost  of  the 
concrete  in  some  proportion  which  must  be  determined  for 
each  individual  case. 

SIZE  OF  AGGREGATE.— The  size  of  aggregate  to  be 
used  depends  upon  the  massiveness  of  the  structure,  its  pur- 
pose, and  whether  or  not  it  is  reinforced.  It  is  seldom  that 
aggregate  larger  than  will  pass  a  3-in.  ring  is  used  and  this 
only  in  very  massive  work.  The  more  usual  size  is  2l/2  ins. 
For  reinforced  concrete  i%  ins.  is  about  the  maximum  size 
allowed  and  in  building  work  i-in.  aggregate  is  most  com- 
monly used.  Some  constructors  use  no  aggregate  larger  than 
24  in.  in  reinforced  building  work,  and  others  require  that 
for  that  portion  of  the  concrete  coming  directly  in  contact 
with  the  reinforcement  the  aggregate  shall  not  exceed  ^4  to 
l/2  in.  The  great  bulk  of  concrete  work  is  done  with  aggre- 
gate smaller  than  2  ins.,  and  as  a  general  thing  where  the 
massiveness  of  the  structure  will  allow  of  much  larger  sizes 
it  will  be  more  economic  to  use  rubble  concrete.  (See  Chap- 
ter VI.) 

COST  OF  AGGREGATE.— The  locality  in  which  the 
work  is  done  determines  the  cost  of  the  aggregate.  Concerns 
producing  broken  stone  or  screened  and  washed  gravel  for 
concrete  are  to  be  found  within  shipping  distance  in  most 
sections  of  the  country  so  that  these  materials  may  be  pur- 
chased in  any  amount  desired.  The  cost  will  then  be  the 
market  price  of  the  material  f.  o.  b.  cars  at  plant  plus  the 
freight  rates  and  the  cost  of  unloading  and  haulage  to  the 
stock  piles.  If  the  contractor  uses  a  local  stone  or  gravel  the 
aggregate  cost  will  be,  for  stone  the  costs  of  quarrying  and 
crushing  and  transportation,  and,  for  gravel,  the  cost  of  exca- 
vation, screening,  washing  and  transportation. 

SCREENED  OR  CRUSHER-RUN  STONE  FOR  CON- 
CRETE.— Formerly  engineers  almost  universally  demanded 
that  broken  stone  for  concrete  should  have  all  the  finer  parti- 
cles screened  out.  This  practice  has  been  modified  to  some 
considerable  extent  in  recent  years  by  using  all  the  crusher 
product  both  coarse  and  fine,  or,  as  it  is  commonly  expressed, 
by  using  run-of-crusher  stone.  The  comparative  merits  of 
screened  and  crusher-run  stone  for  concrete  work  are  ques- 


!6  CONCRETE    CONSTRUCTION. 

tions  of  comparative  economy  and  convenience.  The  fine 
stone  dust  and  chips  produced  in  crushing  stone  are  not,  as 
was  once  thought,  deleterious;  they  simply  take  the  place 
of  so  much  of  the  sand  which  would,  were  the  stone  screened, 
be  required  to  balance  the  sand  and  stone  mixture.  It  is 
seldom  that  the  proportion  of  chips  and  dust  produced  in 
crushing  stone  is  large  enough  to  replace  the  sand  constituent 
entirely;  some  sand  has  nearly  always  to  be  added  to  run-of- 
crusher  stone  and  it  is  in  determining  the  amount  of  this 
addition  that  uncertainty  lies.  The  proportions  of  dust  and 
chips  in  crushed  stone  vary  with  the  kind  of  stone  and  with 
the  kind  of  crusher  used.  Furthermore/  when  run-of-crusher 
stone  is  chuted  from  the  crusher  into  a  bin  or  pile  the  screen- 
ings and  the  coarse  stones  segregate.  Examination  of  a 
crusher-run  stone  pile  will  show  a  cone-shaped  heart  of  fine 
material  enclosed  by  a  shell  of  coarser  stone,  consequently 
when  this  pile  of  stone  is  taken  from  to  make  concrete  a  uni- 
form mixture  of  fine  and  coarse  particles  is  not  secured,  the 
material  taken  from  the  outside  of  the  pile  will  be  mostly 
coarse  and  that  from  the  inside  mostly  fine.  This  segregation 
combined  with  the  natural  variation  in  the  crusher  product 
makes  the  task  of  adding  sand  and  producing  a  balanced  sand 
and  stone  mixture  one  of  extreme  uncertainty  and  some  diffi- 
culty unless  considerable  expenditure  is  made  in  testing  and 
reproportioning.  When  the  product  of  the  crusher  is  screened 
the  task  of  proportioning  the  sand  to  the  stone  is  a  straight- 
forward operation,  and  the  screened  out  chips  and  dust  can 
be  used  as  a  portion  of  the  sand  if  desired.  The  only  saving, 
then,  in  using  crusher-run  stone  direct  is  the  very  small  one  of 
not  having  to  screen  out  the  fine  material.  The  conclusion 
must  be  that  the  economy  of  unscreened  stone  for  concrete 
is  a  very  doubtful  quantity,  and  that  the  risk  of  irregularity 
in  unscreened  stone  mixtures  is  a  serious  one.  The  engineer's 
specifications  will  generally  determine  for  the  contractor 
whether  he  is  to  use  screened  or  crusher-run  stone,  but  these 
same  specifications  will  not  guarantee  the  regularity  of  the 
resulting  concrete  mixture ;  this  will  be  the  contractor's  bur- 
den and  if  the  engineer's  inspection  is  rigid  and  the  crusher- 
run  product  runs  uneven  for  the  reasons  given  above  it  will 


MATERIALS    FOR    CONCRETE.  17 

be  a  burden  of  considerable  expense.  The  contractor  will  do 
well  to  know  his  product  or  to  know  his  man  before  bidding 
less  or  even  as  little  on  crusher-run  as  on  screened  stone 
concrete. 

COST  OF  QUARRYING  AND  CRUSHING  STONE.— 

The  following  examples  of  the  cost  of  quarrying  and  crush- 
ing stone  are  fairly  representative  of  the  conditions  which 
would  prevail  on  ordinary  contract  work.  In  quarrying  and 
crushing  New  Jersey  trap  rock  with  gyratory  crushers  the  fol- 
lowing was  the  cost  of  producing  200  cu.  yds.  per  day : 

Per  day.  Per  cu.  yd. 

3  drillers  at  $275  $     8.25  $0.041 

3  helpers  at  $1.75  5-^5  °-°26 

10  men  barring  out  and  sledging   ....      15.00  0.075 

14  men  loading  carts    21.00  0.105 

4  cart  horses 6.00  0.030 

2  cart  drivers    3.00  0.015 

2  men    dumping    carts    and    feeding 

crusher    3.00  0.015 

i   fireman  for  drill  boiler 2.50  0.013 

I   engineman  for  crusher 3.00  0.015 

i  blacksmith 3-°°  °-OI5 

i  blacksmith    helper    2.00  o.oio 

1  foreman    5-°°  °-O25 

2  tons  coal  at  $3.50 , ...  7-°°  °-°35 

150  Ibs.  40%  dynamite  at  15  cts 22.50  0.113 

Total $106.50  $0.533 

The  quarry  face  worked  was  12  to  18  ft.,  and  the  stone  was 
crushed  to  2-in.  size.  Owing  to  the  seamy  character  of  the 
rock  it  was  broken  by  blasting  into  comparatively  small 
pieces  requiring  very  little  sledging.  The  stone  was  loaded 
into  one-horse  dump  carts,  the  driver  taking  one  cart  to  the 
crusher  while  the  other  was  being  loaded.  The  haul  was 
100  ft.  The  carts  were  dumped  into  an  inclined  chute  leading 
to  a  No.  5  Gates  crusher.  The  stone  was  elevated  by  a 
bucket  elevator  and  screened.  All  stone  larger  than  2  ins. 
was  returned  through  a  chute  to  a  No.  3  Gates  crusher  for 


jg  CONCRETE    CONSTRUCTION. 

recrushing.  The  cost  given  above  does  not  include  interest, 
depreciation,  and  repairs ;  these  items  would  add  about  $8  to 
$10  more  per  day  or  4  to  5  cts.  per  cubic  yard. 

In  quarrying  limestone,  where  the  face  of  the  quarry  was 
only  5  to  6  ft.  high,  and  where  the  amount  of  stripping  was 
small,  one  steam  drill  was  used.  This  drill  received  its  steam 
from  the  same  boiler  that  supplied  the  crusher  engine.  The 
drill  averaged  60  ft.  of  hole  drilled  per  lo-hr.  day,  but  was 
poorly  handled  and  frequently  laid  off  for  repairs.  The  cost 
of  quarrying  and  crushing  was  as  follows : 

Quarry.  Crusher. 

i    driller    $  2.50      i    engineman    $  2.50 

i    helper    1.50      2  men  feeding  crusher.      3.50 

i  man  stripping 1.50     6  men  wheeling   9.00 

4  men  qarrying   6.00      i  bin  man   1.50 

i  blacksmith 2.50      i  general  foreman    ....     3.00 

1/8  ton  coal  at  $3 i.oo      1/3   ton   coal  at  $3....      i.oo 

Repairs  to  drill 60      i   gallon  oil   • 25 

Hose,  drill  steel  and  in-  Repairs   to   crusher.  ...      i.oo 

terest  on  plant 90      Repairs    to    engine    and 

24  Ibs.   dynamite 3.60         boiler    i.oo 

Interest   on   plant i.oo 

Total    ...$20.10 

Total    $23.75 

Summary: 

Per 'day.  Per.  cu.  yd. 

Quarrying $20.10  $0.37 

Crushing    23.75  0.39 


Total  for  60  cu.  yds $43.85  $0.76 

The  "4  men  quarrying"  barred  out  and  sledged  the  stone  to 
sizes  that  would  enter  a  9xi6-in.  jaw  crusher.  The  "6  men 
wheeling"  delivered  the  stone  in  wheelbarrows  to  the  crusher 
platform,  the  run  plank  being  never  longer  than  150  ft.  Two 
men  fed  the  stone  into  the  crusher,  and  a  bin-man  helped  load 
the  wagons  from  the  bin,  and  kept  tally  of  the  loads.  The 
stone  was  measured  loose  in  the  wagons,  and  it  was  found 
that  the  average  load  was  il/2  cu.  yds.,  weighing  2,400  Ibs. 
per  cu.  yd.  There  were  40  wagon  loads,  or  60  cu.  yds. 


MATERIALS    1'OR    CONCRETE.  19 

crushed  per  ic-hr.  day,  althougn  on  some  days  as  high  as 
75  cu.  yds.  were  crushed.  The  stone  was  screened  through 
a  rotary  screen,  9  ft.  long,  having  three  sizes  of  openings,  l/2- 
in.,  i^-in.  and  2/I4-m.  The  output  was  16%  of  the  smallest 
size,  24%  of  the  middle  size,  and  60%  of  the  large  size.  All 
tailings  over  2l/2  ins.  in  size  were  recrushed. 

It  will  be  noticed  that  the  interest  on  the  plant  is  quite  an 
important  item.  This  is  due  to  the  fact  that,  year  in  and 
year  out,  a  quarrying  and  crushing  plant  seldom  averages 
more  than  100  days'  actually  worked  per  year,  and  the  total 
charge  for  interest  must  be  distributed  over  these  100  days, 
and  not  over  300  days  as  is  so  commonly  and  erroneously  done. 
The  cost  of  stripping  the  earth  off  the  rock  is  often  consider- 
ably in  excess  of  the  above  given  cost,  and  each  case  must  be 
estimated  separately.  Quarry  rental  or  royalty  is  usually  not 
in  excess  of  5  cts.  per  cu.  yd.,  and  frequently  much  less.  The 
dynamite  used  was  40%,  and  the  cost  of  electric  exploders  is 
included  in  the  cost  given.  Where  a  higher  quarry  face  is 
used  the  cost  of  drilling  and  the  cost  of  explosives  per  cu.  yd. 
is  less.  Exclusive  of  quarry  rent  and  heavy  stripping  costs, 
a  contractor  should  be  able  to  quarry  and  crush  limestone  or 
sandstone  for  not  more  than  75  cts.  per  cu.  yd.,  or  62  cts.  per 
ton  of  2,000  Ibs.,  wages  and  conditions  being  as  above  given. 

The  labor  cost  of  erecting  bins  and  installing  a  9x16  jaw 
crusher,  elevator,  etc.,  averages  about  $75,  including  hauling 
the  plant  two  or  three  miles,  and  dismantling  the  plant  when 
work  is  finished. 

The  following  is  a  record  of  the  cost  of  crushing  stone  and 
cobbles  on  four  jobs  at  Newton,  Mass.,  in  1891.  On  jobs 
A  and  B  the  stone  was  quarried  and  crushed ;  on  jobs  C  and 
D  cobblestones  were  crushed.  A  9x15-^1.  Farrel-Marson- 
don  crusher  was  used,  stone  being  fed  in  by  two  laborers.  A 
rotary  screen  having  l/2,  I  and  2:/>-in.  openings  delivered  the 
stone  into  bins  having  four  compartments,  the  last  receiving 
the  "tailings"  which  had  failed  to  pass  through  the  screen. 
The  broken  stone  was  measured  in  carts  as  they  left  the  bin, 
but  several  cart  loads  were  weighed,  giving  the  following 
weights  per  cubic  foot  of  broken  stone: 


2O 


CONCRETE    CONSTRUCTION. 


-Size.- 


Ibs. 

Greenish  trap  rock,  "A" 95.8 

Conglomerate,   "B"    IGI.O 

Cobblestones,  "C"  and  "D91.  .  .102.5 


i -in.  2 1/2 -ins.  Tailings. 
Ibs.          Ibs.          Ibs. 
84.3         88.3         91.0 
87.7         94.4 
98.0         99.6 


A  one-horse  cart  held  26  to  28  en.  ft.  (average  I  cu.  yd.) 
of  broken  stone;  a  two-horse  cart,  40  to  42  cu.  ft.,  at  the 
crusher. 


-Job.- 


A.  B. 

Hours  run    412  144 

Short  tons  per  hour 9.0  11.2 

Cu.  yds.  per  hour 7.7  8.9 

Per  cent  of  tailings   31.8  29.3 

Per  cent  of  2^-in.  stone 51.3  51.9 

Per  cent  of  i-in.  stone 10.2  .... 

Per  cent  of  }/2-in.  stone  or  dust.  6.7 


C. 
101 

157 
11.8 

17-5 


A. 


1 8.8        25.5 
—Job.— 
B.  C. 


D. 
198 

12. 1 

9.0 

20.5 


234 


D. 


Explosives,    coal   for    drill    and 

repairs    $0.084  $0.018  

Labor  steam  drilling  0.092  ....  ....  .... 

Labor  hand  drilling 0.249  ....  .... 

Sharpening  tools    0.069  •    0.023  . .  „ .  .... 

Sledging  stone  for  crusher.  .  .  .   0.279  0.420  ....  .... 

Loading  carts    0.098  0.127  ....  $0.144 

Carting  to  crusher   0.072  0.062  $0.314  0.098 

Feeding  crusher   °-°53  °-°53  °-°33  0.065 

Engineer  of  crusher 0.031  0.038  0.029  0.036 

Coal  for  crusher   . 0.079  0.050  0.047  0.044 

Repairs  to  crusher 0.041  .  .  .  .  '  ....  o.on 

Moving  portable  crusher 0.023  •  •  •  •  0.019 

Watchman  ($1.75  a  day) 0-053  0.022  0.030 

Total  cost  per  cu.  yd $0.898  $1.116  $0.445  $0447 

Total  cost  per  short  ton °-745  0.885  °-33°  0.372 


MATERIALS    FOR    CONCRETE.  21 

Note. — "A"  was  trap  rock;  "B"  was  conglomerate  rock'  "C"  and  "D" 
were  trap  and  granite  cobblestones.  Common  laborers  on  jobs  "A"  and 
"D"  were  paid  $1.75  per  9-hr,  day;  on  jobs  "B"  and  "C,"  $1  50  per  9-hr 
day;  two-horse  cart  and  driver,  $5  per  day;  blacksmith,  $2.50;  engineer  on 
crusher,  $2  on  job  "A,  $2.25  on  "B,"  $2.00  on  "C,"  $2.50  on  "D"-  steam 
driller  received  $3,  and  helper  $1.75  a  day;  foreman,  $3  a  day.  Coal  was 
$5.25  per  short  ton.  Forcite  powder,  11  1-3  cts.  per  Ib. 

For  a  full  discussion  of  quarrying  and  crushing  methods 
and  costs  and  for  descriptions  of  crushing  machinery  and 
plants  the  reader  is  referred  to  "Rock  Excavation;  Methods 
and  Cost,"  by  Halbert  P.  Gillette. 

SCREENING  AND  WASHING  GRAVEL.— Handwork 
is  resorted  to  in  screening  gravel  only  when  the  amount  to  be 
screened  is  small  and  when  it  is  simply  required  to  separate 
the  fine  sand  without  sorting  the  coarser  material  into  sizes. 
The  gravel  is  shoveled  against  a  portable  inclined  screen 
through  which  the  sand  drops  while  the  pebbles  slide  down 
and  accumulate  at  the  bottom.  The  cost  of  screening  by  hand 
is  the  cost  of  shoveling  the  gravel  against  the  screen  divided 
by  the  number  of  cubic  yards  of  saved  material.  In  screening 
gravel  for  sand  the  richer  the  gravel  is  in  fine  material  the 
cheaper  will  be  the  cost  per  cubic  yard  for  screening;  on  the 
contrary  in  screening  gravel  for  the  pebbles  the  less  sand  there 
is  in  the  gravel  the  cheaper  will  be  the  cost  per  cubic  yard 
for  screening.  The  cost  of  shoveling  divided  by  the  number 
of  cubic  yards  shoveled  is  the  cost  of  screening  only  Avhen 
both  the  sand  and  the  coarser  material  are  saved.  Tests  made 
in  the  pit  will  enable  the  contractor  to  estimate  how  many 
cubic  yards  of  gravel  must  be  shoveled  to  get  a  cubic  yard  of 
sand  or  pebbles.  An  energetic  man  will  shovel  about  25  cu. 
yds.  of  gravel  against  a  screen  per  lo-hour  day  and  keep  the 
screened  material  cleared  away,  providing  no  carrying  is 
necessary. 

A  mechanical  arrangement  capable  of  handling  &  consider- 
ably larger  yardage  of  material  is  shown  by  Fig.  8.  Two  men 
and  a  team  are  required.  The  team  is  attached  to  the  scraper 
by  means  of  the  rope  passing  through  the  pulley  at  the  top 
of  the  incline.  The  scraper  is  loaded  in  the  usual  manner, 
hauled  up  the  incline  until  its  wheels  are  stopped  by  blocks 
and  then  the  team  is  backed  up  to  slacken  the  rope  and  per- 
mit the  scraper  to  tip  and  dump  its  load.  The  trip  holding  the 
scraper  while  dumping  is  operated  from  the  ground.  The 


22 


CONCRETE    CONSTRUCTION. 


scraper  load  falls  onto  an  inclined  screen  which  takes  out  the 
sand  and  delivers  the  pebbles  into  the  wagon.  By  erecting 
bins  to  catch  the  sand  and  pebbles  this  same  arrangement 
could  be  made  continuous  in  operation. 

In  commercial  gravel  mining,  the  gravel  is  usually  sorted 
into  several  sizes  and  generally  it  is  washed  as  well  as 
screened.  Where  the  pebbles  run  into  larger  sizes  a  crushing 
plant  is  also  usually  installed  to  reduce  the  large  stones. 
Works  producing  several  hundred  cubic  yards  of  screened 
and  washed  gravel  per  day  require  a  plant  of  larger  size  and 
greater  cost  than  even  a  very  large  piece  of  concrete  work  will 


^Ordinary  pulley 


Fig.   8. — Device  for  Excavating  and  Screening  Gravel  and  Loading  Wagons. 

warrant,  so  that  only  general  mention  will  be  made  here  of 
such  plants.  The  commercial  sizes  of  gravel  are  usually 
2-in.,  i-in.,  1/2-111.  and  ^4-in.,  down  to  sand.  No  very  detailed 
costs  of  producing  gravel  by  these  commercial  plants  are 
available.  At  the  plant  of  the  Lake  Shore  &  Michigan  South- 
ern Ry.,  where  gravel  is  screened  and  washed  for  ballast,  the 
gravel  is  passed  over  a  2-in.,  a  ^-in.,  a  *4-in.  and  a  l/s-in. 
screen  in  turn  and  the  fine  sand  is  saved.  About  2,000  tons 
are  handled  per  day;  the  washed  gravel,  2-in.  to  >^-in.  sizes, 
represents  from  40  to  65  per  cent,  of  the  raw  gravel  and  costs 
from  23  to  30  cts.  per  cu.  yd.,  for  excavation,  screening  and 


MATERIALS    FOR    CONCRETE. 


washing.  The  drawings  of  Fig.  9  show  a  gravel  washing 
plant  having  a  capacity  of  120  to  130  cu.  yds.  per  hour,  oper- 
ated by  the  Stewart-Peck  Sand  Co.,  of  Kansas  City,  Mo. 
Where  washing  alone  is  necessary  a  plant  of  one  or  two 
washer  units  like  those  here  shown  could  be  installed  without 
excessive  cost  by  a  contractor  at  any  point  where  water  is 


—Elevator 


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NEWS.        £!£ 

Plan 

Fig.  9.— Gravel  Washing  Plant  of  120  to  130  Cu.   Yds.,   Per  Hour  Capacity. 

available.  Each  washer  unit  consists  of  two  hexagonal 
troughs  18  ins.  in  diameter  and  18  ft.  long.  A  shaft  carrying 
blades  set  spirally  is  rotated  in  each  trough  to  agitate  the 
gravel  and  force  it  along ;  each  trough  also  has  a  fall  of  6  ins. 
toward  its  receiving  end.  The  two  troughs  are  inclosed  in  a 
tank  or  box  and  above  and  between  them  is  a  5-in.  pipe  having 


24  CONCRETE    CONSTRUCTION. 

24~in.  holes  3  ins.  apart  so  arranged  that  the  streams  are 
directed  into  the  troughs.  The  water  and  dirt  pass  off  at  the 
lower  end  of  the  troughs  while  the  gravel  is  fed  by  the  screws 
into  a  chute  discharging  into  a  bucket  elevator,  which  in  turn 
feeds  into  a  storage  bin.  The  gravel  to  be  washed  runs  from 
2  ins.  to  l/%  in.  in  size;  it  is  excavated  by  steam  shovel  and 
loaded  into  il/>  cu.  yd.  dump  cars,  three  of  which  are  hauled 
by  a  mule  to  the  washers,  where  the  load  is  dumped  into  the 
troughs.  The  plant  having  a  capacity  of  120  to  130  cu.  yds. 
per  hour  cost  $25,000,  including  pump  and  an  8-in.  pipe  line 
a  mile  long.  A  loo-hp.  engine  operates  the  plant,  and  20  men 
are  needed  for  all  purposes.  This  plant  produces  washed 
gravel  at  a  profit  for  40  cts.  per  cu.  yd. 


CHAPTER  II. 

THEORY  AND  PRACTICE  OF  PROPORTIONING 
CONCRETE. 

American  engineers  proportion  concrete  mixtures  by  meas- 
ure, thus  a  1-3-5  concrete  is  one  composed  of  i  volume  of 
cement,  3  volumes  of  sand  and  5  volumes  of  aggregate.  In 
Continental  Europe  concrete  is  commonly  proportioned  by 
weight  and  there  have  been  prominent  advocates  of  this  prac- 
tice among  American  engineers.  It  is  not  evident  how  such 
a  change  in  prevailing  American  practice  would  be  of  prac- 
tical advantage.  Aside  from  the  fact  that  it  is  seldom  con- 
venient to  weigh  the  ingredients  of  each  batch,  sand,  stone 
and  gravel  are  by  no  means  constant  in  specific  gravity,  so 
that  the  greater  exactness  of  proportioning  by  weight  is  not 
apparent.  In  this  volume  only  incidental  attention  is  given 
to  gravimetric  methods  of  proportioning  concrete. 

VOIDS. — Both  the  sand  and  the  aggregates  employed  for 
concrete  contain  voids.  The  amount  of  this  void  space  de- 
pends upon  a  number  of  conditions.  As  the  task  of  propor- 
tioning concrete  consists  in  so  proportioning  the  several  ma- 
terials that  all  void  spaces  are  filled  with  finer  material  the 
conditions  influencing  the  proportion  of  voids  in  sand  and 
aggregates  must  be  known. 

Voids  in  Sand.— The  two  conditions  exerting  the  greatest 
influence  on  the  proportion  of  voids  in  sand  are  the  presence 
of  moisture  and  the  size  of  the  grains  of  which  the  sand  is 
composed. 

The  volume  of  sand  is  greatly  affected  by  the  presence  of 
varying  percentages  of  moisture  in  the  sand.  A  dry  loose  sand 
that  has  45  per  cent,  voids  if  mixed  with  5  per  cent,  by  weight 
of  water  will  swell,  unless  tamped,  to  such  an  extent  that  its 

25 


26  CONCRETE    CONSTRUCTION. 

voids  may  be  57  per  cent.  The  same  sand  if  saturated  with 
water  until  it  becomes  a  thin  paste  may  show  only  37^  per 
cent,  voids  after  the  sand  has  settled.  Table  I  shows  the 

TABLE  I. — SHOWING  EFFECT  OF  ADDITIONS  OF  DIFFERENT  PER- 
CENTAGES OF  MOISTURE  ON  VOLUME  OF  SAND. 

Per  cent  of  water  in  sand       00.5          1  2           3           5  10 

Weight  per  cu.  yd.  of  fine     Lbs.      Lbs.  Lbs.,  Lbs.  Lbs.  Lbs.  Lbs. 

sand  and  water 3,457    2,206  2,085  2,044  2,037  2,035  2,133 

Weight  per  cu.yd.of  coarse 

sand  and  water 2,551    2,466  2,380  2,122  2,058  2,070  2,200 

results  of  tests  made  by  Feret,  the  French  experimenter.  Two 
kinds  of  sand  were  used,  a  very  fine  sand  and  a  coarse  sand. 
They  were  measured  in  a  box  that  held  2  cu.  ft.  and  was  8  ins. 
deep,  the  sand  being  shoveled  into  the  box  but  not  tamped  or 
shaken.  After  measuring  and  weighing  the  dry  sand  0.5  per 
cent,  by  weight  of  water  was  added  and  the  sand  was  mixed 
and  shoveled  back  into  the  box  again  and  then  weighed. 
These  operations  were  repeated  with  varying  percentages  of 
water  up  to  10  per  cent.  It  will  be  noted  that  the  weight  of 
mixed  water  and  sand  is  given ;  to  ascertain  the  exact  weight 
of  dry  sand  in  any  mixture,  divide  the  weight  given  in  the 
table  by  100  per  cent,  plus  the  given  tabular  per  cent. ;  thus  the 
weight  of  dry,  fine  sand  in  a  5  per  cent,  mixture  is 
2,035-^-1.05=1,938  Ibs.  per  cu.  yd.  The  voids  in  the  dry 
sand  were  45  per  cent,  and  in  the  sand  with  5  per  cent, 
moisture  they  were  56.7  per  cent.  Pouring  water  onto  loose, 
dry  sand  compacts  it.  By  mixing  fine  sand  and  water-  to  a 
thin  paste  and  allowing  it  to  settle,  it  was  found  that  the 
sand  occupied  n  per  cent,  less  space  than  when  measured 
dry.  The  voids  in  fine  sand,  having  a  specific  gravity  of  2.65, 
were  determined  by  measurement  in  a  quart  measure  and 
found  to  be  as  follows : 

Sand  not  packed,  per  cent,  voids 44^ 

Sand  shaken  to  refusal,  per  cent,  voids   35 

Sand  saturated  with  water,  per  cent  voids 37//2 

Another  series  of  tests  made  by  Air.  H.  P.  Boardman,  using 
Chicago  sand  having  34  to  40  per  cent,  voids,  showed  the 
following  results: 

Water  added,  per  cent *...     2.46         8       ic 

Resulting  per  cent,  increase 17.6     22     19.5     16.6     15.6 

Mr.  Wm.  B.  Fuller  found  by  tests  that  a  dry  sand,  .having 


PROPORTIONING   CONCRETE.  27 

34  per  cent,  voids,  shrunk  9.6  per  cent,  in  volume  upon  thor- 
ough tamping  until  it  had  27  per  cent,  voids.  The  same  sand 
moistened  with  6  per  cent,  water  and  loose  had  44  per  cent, 
voids,  which  was  reduced  to  31  per  cent,  by  ramming.  The 
same  sand  saturated  with  water  had  33  per  cent,  voids  and 
by  thorough  ramming  its  volume  was  reduced  Sl/2  per  cent 
until  the  sand  had  only  26l/2  per  cent,  voids.  Further  experi- 
ments might  be  quoted  and  will  be  found  recorded  in  several 
general  treatises  on  concrete,  but  these  are  enough  to  demon- 
strate conclusively  that  any  theory  of  the  quantity  of  cement 
in  mortar  to  be  correct  must  take  into  account  the  effect  of 
moisture  on  the  voids  in  sand. 

The  effect  of  the  size  and  the  shape  of  the  component  grains 
on  the  amount  of  voids  in  sand  is  considerable.  Feret's  ex- 
periments are  conclusive  on  these  points,  and  they  alone  will 
be  followed  here.  Taking  for  convenience  three  sizes  of  sand 
Feret  mixed  them  in  all  the  varying  proportions  possible  with 
a  total  of  10  parts ;  there  were  66  mixtures.  The  sizes  used 
were:  Large  (L),  sand  composed  of  grains  passing  a  sieve 
of  5  meshes  per  linear  inch  and  retained  on  a  sieve  of  15 
meshes  per  linear  inch;  medium  (M),  sand  passing  a  sieve  of 
15  meshes  and  retained  on  a  sieve  of  50  meshes  per  linear  inch, 
and  fine  (F),  sand  passing  a  5O-mesh  sieve.  With  a  dry  sand 
whose  grains  have  a  specific  gravity  of  2.65,  the  weight  of  a 
cubic  yard  of  either  the  fine,  or  the  medium,  or  the  large  size, 
was  2,190  Ibs.,  which  is  equivalent  to  51  per  cent,  voids.  The 
greatest  weight  of  mixture,  2,840  Ibs.  per  cu.  yd.,  was  an 
L0Af0F4  mixture,  that  is,  one  composed  of  six  parts  large,  no 
parts  medium  and  4  parts  fine;  this  mixture  was  the  densest 
of  the  66  mixtures  made,  having  36  per  cent,  voids.  It  will  be 
noted  chat  the  common  opinion  that  the  densest  mixture  is 
obtained  by  a  mixture  of  gradually  increasing  sizes  of  grains 
is  incorrect ;  there  must  be  enough  difference  in  the  size  of 
the  grains  to  provide  voids  so  large  that  the  smaller  grains 
will  enter  them  and  not  wedge  the  larger  grains  apart.  Turn- 
ing now  to  the  shape  of  the  grains,  the  tests  showed  that 
rounded  grains  give  less  voids  than  angular  grains.  Using 
sand  having  a  composition  of  L5M3F2  Feret  got  the  following 
results : 


28 


CONCRETE    CONSTRUCTION. 


Kind  of   Grains. 

Natural  sand,  rounded  grains 

Crushed  quartzite,  angular  grains, 
Crushed  shells,  flat  grains.  . .  /.I 
Residue  of  quartzite,  flat  grains.  . 


—Per  cent.  Voids. — 
Shaken.         Unshaken. 


25.6 
27.4 
31.8 
34-6 


35-9 
42.1 

44-3 
47-5 


The  sand  was  shaken  until  no  further  settlement  occurred. 
It  is  plain  from  these  data  on  the  effect  of  size  and  shape 
of  grains  on  voids  why  it  is  that  discrepancies  exist  in  the 
published  data  on  voids  in  dry  sand.  An  idea  of  the  wide 
variation  in  the  granulometric  composition  of  different  sands 
is  given  by  Table  II.  Table  III  shows  the  voids  as  deter- 
mined for  sands  from  different  localities  in  the  United  States. 
TABLE  II.  —  SHOWING  GRANULOMETRIC  COMPOSITIONS  OF  DIFFERENT 

SANDS. 


Held  by  L  Sieve. 
No.  10 
No.  20 
No.  30 
No.  40 
No.  50 
No.  100 
No.  200.  .  . 


A 

35.3% 
32.1 
14.6 


4.9 
2.0 


12.8% 
40.0 

29  3 
5.7 
2.3 


4.2% 
12.5 
44.4 


11% 
14 

53" 


Voids 33%  39%  41.7%          31% 

NOTE. — A,  is  a  "fine  gravel"  (containing  8%  clay)  used  at  Philadelphia. 
B,  Delaware  River  sand.  C,  St.  Mary's  River  sand.  D,  Green  River,  Ky., 
sand,  "clean  and  sharp." 

TABLE  III. — SHOWING  MEASURED  VOIDS  IN  ^AND  FROM  DIFFERENT 

LOCAILTIES. 

Percent 

Authority. 

W.  M.  Hall 

C.  E.  Sherman 

C.  E.  Sherman 

S.  B.  Newberry 

H.  H.  Henby 

H.  von  Schon 

H.  P.  Broadman 


Locality. 

Ohio  River 

Sandusky,  O 

Franklin' Co.,  O 

Sandusky  Bay.,  O 

St.  Louis,  Mo 

Sault  Ste.  Marie 

Chicago,  111 

Philadelphia,  Pa 

Mass.  Coast 

Boston,  Mass 

Cow  Bay,  L.  I 

Little  Falls,  N.  J 

Canton,  111, 


Geo.  A.  Kimball 

Myron  S.  Falk 

W.  B.  Fuller 

G.  W.  Chandler 


Voids. 
31 
40 
40 
32.3 

Remarks. 
Washed 
Lake 
Bank 

34.3 

41.7 
34  to  40 

Miss.  River 
River 

39 
31  to  34 

Del.  River 

33  - 
404 

Clean 

45  6 

30 

Clean 

Voids  in  Broken  Stone  and  Gravel. — The  percentage  of 
voids  in  broken  stone  varies  with  the  nature  of  the  stone: 
whether  it  is  broken  by  hand  or  by  crushers ;  with  the  kind  of 
crusher  used,  and  upon  whether  it  is  screened  or  crusher-run 


.. 

PROPORTIONING   CONCRETE.  29 

product.  The  voids  in  broken  stone  seldom  exceed  52  per 
cent,  even  when  the  fragments  are  of  uniform  size  and  the 
stone  is  shoveled  loose  into  the  measuring  box.  The  follow- 
ing records  of  actual  determinations  of  voids  in  broken  ston^ 
cover  a  sufficiently  wide  range  of  conditions  to  show  about 
the  limits  of  variation. 

The  following  are  results  of  tests  made  by  Mr.  A.  N.  John- 
son, State  Engineer  of  Illinois,  to  determine  the  variation  in 
voids  in  crushed  stone  due  to  variation  in  size  and  to  method 
of  loading  into  the  measuring  box.  The  percentage  of  voids 
was  determined  by  weighing  the  amount  of  water  added  to 
fill  the  box: 

Method  of  Per  cent. 

Size.  Loading.  of  \  oids. 

3      in.         2O-ft.  drop   41.8 

3      in.         15-ft  drop    46.8 

3      in.         15-ft.  drop    47.2 

3      in.         Shovels 48.7 

ll/2  in.         2O-ft.   drop 42.5 

1 1/2  in.          15-ft.   drop    46.8 

il/2  in.         15-ft.  drop    46.8 

1 3/2  in.         Shovels 50.5 

j/4  in.         2O-ft.  drop 39.4 

y±  in.         15-ft.  drop   42.7 

y4  in.          15-ft.   drop    41.5 

24  in.         15-ft.  drop    41.8 

%  in.         Shovels    45.2 

3/4  in.         Shovels    44.6 

y%  in.         Shovels    41.0 

y%  in.         Shovels    4°-6 

y%  in.         Shovels    '.     41-0 

The  table  shows  clearly  the  effect  on  voids  of  compacting 
the  stone  by  dropping  it;  it  also  shows  for  the  fom.  and  the 
^-in.  stone  loaded  by  shovels  how  uniformly  the  percentages 
of  voids  run  for  stone  of  one  size  only.  Dropping  the  stone 
20  ft.  reduced  the  voids  some  12  to  15  per  cent,  as  compared 
with  shoveling. 

Table  IV  gives  the  voids  in  broken  stone  as  determined  by 
various  engineers ;  it  requires  no  explanation.  Table  V, 


CONCRETE    CONSTRUCTION. 


TABLE  IV.  —  SHOWING  DETERMINED  PERCENTAGES  OF  VOIDS  IN 
BROKEN  STONE  FROM  VARIOUS  COMMON  ROCKS. 


Authority. 

Percent 
Voids. 

Remarks. 

Sabin 

49.0 

Limestone  crusher  run  after  screening  out 

44.0 

|-in.  and  under. 
Limsetone  (1  part  screenings  mixed  with 

Wm.  M.  Black.. 

46.5 

6  parts  broken  stone)  . 
Screened  and  washed,  2-ins.  and  under. 

J  J   R  Croes 

47  5 

Gneiss  after  screening  out  J-in.  and  under. 

S  B   Newberry  .  . 

47  0 

Chiefly  about  egg  size 

H.  P.  Broadman  
Wm  M  Hall 

39  to  42 

48  to  52 
48  0 

Chicago  limestone,  crusher  run. 
screened  into  sizes. 
Green  River  limestone  2^-ins  and  smaller 

Wm.  B.  Fuller.. 
Geo.  A.  Kimball  
Myron  S.  Falk  

50.0 

47.6 

49.5 
48.0 

dust  screened  out. 
Hudson  River  trap,  2^-ins.  and  smaller, 
dust  screened  out. 
New  Jersey  trap,  crusher  run,  £  to  2.1  in. 
Roxbury  conglomerate,  \  to  2^  ins. 
Limestone,  ^  to  3  ins. 

W.  HLHenby  

43.0 
46  0 

2-in  size. 
1  ^-in   size 

Feret  

53  4 

Stone    1  6  to  2  4  ins 

A.  W.  DowV.  !  ...'.... 

51.7 
52.1 
45.3 

0.8  to  1.6  in. 
0.4  to  0.8  in. 
Bluestone,  89%  being  1^  to  2£  ins. 

453 

90%  being  \  to  1^  in 

Taylor  and  Thompson 

G.  W.  Chandler  
Emile  Low  
C.  M.  Saville  

54.5 
54.5 
45.0 
51.2 
40.0 
39.0 
46.0 

Trap,  hard,  1  to  2£  ins. 
"      \  to  1  in. 
"      0  to  1\  ins. 
soft,    |  to  2  ins. 
Canton,  111. 
Buffalo  limestone,  crusher  run,  dust  in. 
Crushed  cobblestone   screened  into  sizes 

TABLE  V. — SHOWING  PERCENTAGES  OF  VOIDS  IN  GRAVEL  AND 
BROKEN  STONE  OF  DIFFERENT  GRAXULOMETRIC 


Passing  a  ring  of . .  .  . 

Held  by  a  ring 

Parts... 


COMPOSITIONS. 


2.4" 
1.6" 

1 

0 

0 

1 

1 

0 

1 

4 

] 

i 

8 


1.6" 
0.8* 

0 

1 

0 

1 

0 

1 
1 
1 

4 
1 
0 


0.8' 
0.4' 

0 

0 

1 

0 

1 

1 

1 
1 
4 
2 


. — Per  cent  Voids  in — 
Round  Broken 

Pebbles.  Stone. 


40.0 
38.8 
41.7 
35.8 
35.6 
37.9 
35.5 
34.5 
36.6 
38.1 
34.1 


53.4 
51.7 
52.1 
50.5 
47.1 
49.5 
47.8 
49.2 
49.4 
48.6 


PROPORTIONING   CONCRETE.  31 

taken  from  Feret's  tests,  shows  the  effect  of  changes  in 
granulometric  composition  on  the  amount  of  voids  in  both 
broken  stone  and  gravel.  Considering  the  column  giving 
voids  in  stone  it  is  to  be  noted  first  how  nearly  equal  the 
voids  are  for  stone  of  uniform  size  whatever  that  size  be. 
As  was  the  case  with  sand  a  mixture  of  coarse  and  fine  par- 
ticles gives  the  fewest  voids ;  for  stone  an  L^M^F^  mixture 
and  for  gravel  an  L8MGF2  mixture.  Tamping  reduces  the 
voids  in  broken  stone.  Mr.  Geo.  W.  Rafter  gives  the  voids  in 
clean,  hand-broken  limestone  passing  a  2^2-in.  ring  as  43  per 
cent,  after  being  lightly  shaken  and  37^  Per  cent,  after  being 
rammed.  Generally  speaking  heavy  ramming  will  reduce  the 
voids  in  loose  stone  about  20  per  cent. 

It  is  rare  that  gravel  has  less  than  30  per  cent,  or  more  than 
45  per  cent,  voids.  If  the  pebbles  vary  considerably  in  size 
so  that  the  small  fit  in  between  the  large,  the  voids  may  be 
as  low  as  30  per  cent,  but  if  the  pebbles  are  tolerably  uniform 
in  size  the  voids  will  approach  45  per  cent.  Table  V  shows 
the  effect  of  granulometric  composition  on  the  voids  in  gravel 
as  determined  by  Feret.  Mr.  H.  Von  Schon  gives  the  follow- 
ing granulometric  analysis  of  a  gravel  having  34.1  per  cent, 
voids : 

Retained  on    i-in.  ring,  per  cent 10.70 

Retained  on  ^-in.  ring,  per  cent 23-65 

Retained  on.No.  4  sieve,  per  cent 8.70 

Retained  on  No.  10  sieve,  per  cent I7-I4 

Retained  on  No.  20  sieve,  per  cent 21.76 

Retained  on  No.  30  sieve,  per  cent 6.49 

Retained  on  No.  40  sieve,  per  cent.  . 5-9^ 

Passed  a  No.  40  sieve,  per  cent 5-59 

Passed  a  i^-in  ring,  per  cent 100.00 

As  mixtures  of  broken  stone  and  gravel  are  often  used  the 
following  determinations  of  voids  in  such  mixtures  are  given. 
The  following  determinations  were  made  by  Mr.  Wm.  M. 
Hall  for  mixtures  of  blue  limestone  and  Ohio  River  washed 
gravel : 


CONCRETE    CONSTRUCTION, 


Per  cent.  Per  cent.  Per  cent. 

Stone.  Gravel.  Voids  in  Mix. 

100  with         o    • 48 

80  20 .          44 

60  40 38^ 

50  '"          50    36 

o  "        100 35 

The  dust  was  screened  from  the  stone  all  of  which  passed 
a  2^2-in.  ring;  the  gravel  all  passed  a  il/2-m.  screen.  Using 
the  same  sizes  of  gravel  and  Hudson  River  trap  rock,  the 
results  were : 

Per  cent.  Per  cent.  Per  cent. 

Trap.  Gravel.  Voids  in  Mix. 

100         with         o   50 

60  40    38^ 

50  "          50    • 36 

o  loo    35 

The  weight  of  a  cubic  foot  of  loose  gravel  or  stone  is  not  an 
accurate  index  of  the  percentage  of  voids  unless  the  specific 
gravity  is  known.  Pure  quartz  weighs  165  Ibs.,  per  cu.  ft., 
hence  broken  quartz  having  40  per  cent,  voids  weighs 
165  X  -60  =  99  Ibs.  per  cu.  ft.  Few  gravels  are  entirely,  quartz, 
and  many  contain  stone  having  a  greater  specific  gravity  like 
some  traps  or  a  less  specific  gravity  like  some  shales  and  sand- 
stone. Tables  VI  and  VII  give  the  specific  gravities  of  com- 
mon stones  and  minerals  and  Table  VIII  gives  the  weights 
corresponding  to  different  percentages  of  voids  for  different 
specific  gravities. 

TABLE  VI. — SPECIFIC  GRAVITY  OF  STONE. 
(Condensed  from  Merrill's  "Stones  for  Building.") 

Trap,  Boston,  Mass 2.78  Limestone,  (oolitic)    Bedford, 

Duluth,  Minn 2. 8  to  3.0                                  Ind 2.  25  to  2. 45 

"     Jersey 'City,  N.  J 3.03  Marquette,  Mich..  2.34 

"      Staten  Island,  N.  Y..       2.86  Glens  Falls,  N.Y.  2.70 

Gneiss,  Madison  Ave.,  N.  Y       2.92  Lake    Champlain, 

Granite,  New  London,  Conn. :  2 . 66                                N.Y 2 . 75 

Greenwich,  Conn. .        2 . 84  Sandstone,  Portland,  Conn. .  .  2 . 64 

Vinalhaven,  Me..  .        2.66  Haverstraw,  N.  Y  2. 13 

Quincy,  Mass 2.66  Medina,  N.  Y.  ...  2.41 

Barre,  Vt 2.65  Potsdam,  N.  Y.  ..  2.60 

Limestone,  Joliet,  111 2.56  (grit)  Berea,  O. . . .  2.12 

Quincy,  111.2.51  to  2.  57 


PROPORTIONING   CONCRETE. 


33 


TABLE  VII. — SPECIFIC  GRAVITY  OF  COMMON  MINERALS  AND  ROCKS. 


Apatite  

2.92-3.25 

Limestone  

2.35-2.87 

Basalt  

3.01 

Magnetite,  Fe3O4..  .  . 

.  .   4.9   -5.2 

Calcite,  CaCo3  

2.5    -2.73 

Marble  

2.08-2.8.ti 

Cassiterite,  SnO.>.  ....... 

6.4    -7.1 

Mica  

2.75-3.1 

Cerrusite,  PbCO3  

6.46-6.48 

Mica  Schist  

.  .    2.5   -2.9 

Chalcopyrite,  CuFeS-^  .  . 

4.1    -4.3 

Olivine  

.  .    3.33-3.5 

Coal,  anthracite  

1.3   -1.84 

Porphyry  '.  .  .V 

.  .    2.5   -2.6 

Coal,  bituminous  

1  2   -1.5 

Pyrite,  FeS2  

.  .    4.83-5.2 

Diabase  

?.C   -3.03 

Quartz,  SiO2  

.    2.5   -2.8 

Diorite  

2.92 

Quartzite  

.  .    2.6   -2.7 

Dolomite,  CaMg  (CO3)*. 

2.8    -2.9 

Sandstone  

2.0   -2.78 

Feldspar  

2.44-2.78 

Medina.  .  . 

.  .    2.4 

Felsite  

2.65 

Ohio  

2.2 

Galena,  Pbs  

7.25-7.77 

Slaty  

'.  '.    1.82 

Garnet  

3.15-4.31 

Shale  

2.4    -2.8 

Gneiss  

2.G2-2.92 

Slate  

2.5    -2.8 

Granite  

2.55-2.86 

Sphalerite,  ZnS.  .  . 

3.9    -4.2 

Gypsum  

2.3    -3.28 

Stibnite,  Sb^Ss  

.'.    4.5    -4.6 

Halite  (salt)  NaCl  

2.1    -2.56 

Syenite  

.  .    2.27-2.65 

Hematite,  Fe-^Og  

4.5    -5.3 

Talc  

.  .    2.56-2.8 

Hornblende  

3.05-3.47 

Trap.  .  .  . 

2.6    -3.0 

Limonite,  Fe3O4  (OH)6. 

3.6    -4.0 

TABLE  VIII. — SHOWING  WEIGHT  OF  STONE  WITH  DIFFERENT 

PERCENTAGES  OF  VOIDS  FOR  DIFFERENT 

SPECIFIC  GRAVITIES. 


'D  > 

4)  rt 


Weight  in  Lbs.  per  cu.  yd.  when  Voids  are 


2.1 
2.2 
2.3 
2.4 
2.5 
2.6 
2.7 
2.8 
2.9 
3.0 
3.1 
3.2 
3.3 
3.4 
3.5 


62.355 
124.7 
130.9 
137.2 
143.4 
149.7 
155.9 
162.1 
168.4 
174.6 
180.9 
187.1 
193.3 
199.5 
205.8 
212.0 
218.3 


1,684 
3,367 
3,536 
3,704 
3,872 
4,041 
4,209 
4,377 
4,546 
4,714 
4,882 
5,051 
5,219 
5,388 
5,556 
5,724 
5,893 


30% 

1,178 
2,357 
2,475 
2,593 
2,711 
2,828 
2,946 
3,064 
3,182 
3,300 
3,418 
3,536' 
3,653 
3,771 
3,889 
4,007 
4,125 


1,094 
2,187 
2,298 
2,408 
2,517 
2,626 
2,736 
2,845 
2,955 
3,064 
3,174 
3,283 
3,392 
3,502 
3,611 
3,721 
3,830 


40% 

45% 

50% 

1,010 

926 

842 

2,020 

1,852 

1,684 

2,121 

1,945 

1,768 

2,222 

2,037 

1,852 

2,323 

2,130 

1,936 

2,424 

2,222 

2,020 

2,525 

2,315 

2,105 

2,626 

2,408 

2,189 

2,727 

2,500 

2,273 

2,828 

2,593 

2,357 

2,929 

2,685 

2,441 

3,030 

2,778 

2,526 

3,131 

2,871 

2,609 

3,232 

2,963 

2,694 

3,333 

3,056 

2,778 

3,434 

3,148 

2,862 

3  535 

3,241 

2,947 

In  buying  broken  stone  by  the  cubic  yard  it  should  be 
remembered  that  hauling  in  a  wagon  compacts  the  stone  by 
shaking  it  down  and  reduces  the  volume.  Table  IX  shows 
the  results  of  tests  made  by  the  Illinois  Highway  Commission 
to  determine  the  settlement. of  crushed  stone  in  wagon  loads 
for  different  lengths  of  haul.  The  road  over  which  the  tests 
were  made  was  a  macadam  road,  not  particularly  smooth,  but 


34 


CONCRETE    CONSTRUCTION. 


might  be  considered  as  an  average  road  surface.  The  wagon 
used  was  one  with  a  dump  bottom  supported  by  chains,  which 
were  drawn  as  tight  as  possible,  so  as  to  reduce  the  sag  to  a 
minimum.  It  will  be  noticed  that  about  50  per  cent,  of  the 
settlement  occurs  within  the  first  100  ft.,  and  75  per  cent,  of 
the  settlement  in  the  first  200  ft.  Almost  all  of  the 
settlement  occurs  during  the  first  half  mile,  as  the  tests 
showed  practically  no  additional  settlement  for  distances 
beyond.  Some  of  the  wagons  were  loaded  from  the  ground 
with  shovels,  others  were  loaded  from  bins,  the  stone  having 
a  15-ft.  drop,  which  compacted  the  stone  a  little  more  than 
where  loaded  with  shovels,  so  that  there  was  somewhat  less 
settlement.  But  at  the  end  of  a  half  mile  the  density  was 
practically  the  same,  whatever  the  method  of  loading.  The 
density  at  the  beginning  and  at  the  end  of  the  haul  can  be 
compared  by  the  weight  of  a  given  volume  of  crushed  stone. 
For  convenience,  the  weight  of  a  cubic  yard  of  the  material 
at  the  beginning  of  the  haul  and  at  the  end  was  computed 
from  the  known  contents  of  a  wagon. 

TABLE  IX. — SHOWING  SETTLEMENT  OF  BROKEN  STONE  DUE  TO 

DIFFERENT  LENGTHS  OF  HAUL  ON  ORDINARILY 

GOOD  ROAD  IN  WAGONS. 


Weight  per 

Per  cent  Settlement  for  Hauling 

Cu   Yd 

in  Lbs. 

Method  of 

bize 

Loading. 

100' 

200' 

300' 

400' 

500' 

600' 

700' 

i  mile 

1  mile 

At 
start. 

At 
finish. 

creenings. 

15  ft.  drop 

11.5 

11.5 

2.518 

2,840 

creenings. 

15  ft.  drop 

12.6 

12.6 

2,518 

2,886 

creenings.  i  15  ft.  drop 

7.3  1   8.3     8.9 

9  2 

9.5  10.1 

10,1 

il.2     

2,450 

2,770 

creenings  . 

15  ft.  drop 

5.0'   9.6 

10.2 

10.2 

10.4   10.4 

10.4 

12.4 

2,425 

2,780 

inch.  .  .  . 

15  ft.  drop 

11.5 

11.5* 

2,305 

2.600 

inch  .... 

15  ft.  drop 

5.3 

ft.  2 

7.1 

7.7 

7.9!   8.0 

8.3 

9.2 

2,380 

2,625 

inch.  .  .  . 

15  ft.  drop 

2.6     3.7 

4.9 

5.3 

53 

5  3 

54 

5.4 

2,450 

2,600 

inch  .... 

Shovels  .  .  . 

3.5     4.1 

4.8 

5.3 

5.3 

5.7 

6.5 

7.25 

2,270 

2,445 

inch   .  .  . 

Shovels  .  .  . 

12  6 

12  6 

2  305 

2  642 

=r=r==^= 

inch  

15  ft.  drop 

— 

_ 

= 

= 

= 

= 

= 

10.1 

10.1 

2,376 

2,638 

inch  
inch  
inch  

15  ft.  drop 
15  ft.  drop 
Shovels  .  . 

3.5 
0.5 

4.2 
2.6 

4.5 

2.8 

4.8 
4.1 

5.0 
4.3 

5.0 

4.3 

5.0 
4.3 

6.0 
4.9 
12  6 

12  6 

2,360 
2,470 
2  270 

2,505 
2,595 
2  601 

inch  

Shovels  .  .  . 

M 

5.6 

6.5 

6.5 

6.8 

6.8 

6.8 

7.1 

2,335 

2,510 

* — Same  per  cent  of  settlement  for  two-mile  haul. 


PROPORTIONING   CONCRETE.  35 

THEORY  OF  THE  QUANTITY  OF  CEMENT  IN 
MORTAR  AND  CONCRETE.— All  sand  contains  a  large 
percentage  of  voids ;  in  i  cu.  ft.  of  loose  sand  there  is  0.3  to 
0.5  cu.  ft.  of  voids,  that  is,  30  to  50  per  cent,  of  the  sand  is 
voids.  In  making  mortar  the  cement  is  mixed  with  the  sand 
and  the  flour-like  particles  of  the  cement  fit  in  between  the 
grains  of  sand  occupying  a  part  or  all  of  the  voids.  The 
amount  of  cement  required  in  a  mortar  will  naturally  depend 
upon  the  amount  of  voids  in  the  particular  sand  with  which 
it  is  mixed  and  since  a  correct  estimate  of  the  number  of 
barrels  of  cement  per  cubic  yard  of  mortar  is  very  important, 
and  since  it  is  not  always  possible  to  make  actual  mixtures 
before  bidding,  rules  based  on  various  theories  have  been 
formulated  for  determining  these  quantities.  In  this  volume 
the  rule  based  on  the  theory  outlined  by  one  of  the  authors  in 
1901  will  be  followed.  The  following  is  a  discussion  of  the 
authors'  theory: 

When  loose  sand  is  mixed  with  water,  its  volume  or  bulk 
is  increased ;  subsequent  jarring  will  decrease  its  volume,  but 
still  leave  a  net  gain  of  about  10  per  cent. ;  that  is,  I  cu.  ft. 
of  dry  sand  becomes  about  i.i  cu.  ft.  of  damp  sand.  Not  only 
does  this  increase  in  the  volume  of  the  sand  occur,  but,  instead 
of  increasing  the  voids  that  can  be  filled  with  cement,  there  is 
an  absolute  loss  in  the  volume  of  available  voids.  This  is 
due  to  the  space  occupied  by  the  water  necessary  to  bring  the 
sand  to  the  consistency  of  mortar;  furthermore,  there  is  sel- 
dom a  perfect  mixture  of  the  sand  and  cement  in  practice, 
thus  reducing  the  available  voids.  It  is  safe  to  call  this  reduc- 
tion in  available  voids  about  10  per  cent. 

When  loose,  dry  Portland  cement  is  wetted,  it  shrinks  about 
15  per  cent,  in  volume,  behaving  differently  from  the  sand, 
but  it  never  shrinks  back  to  quite  as  small  a  volume  as  it 
occupies  when  packed  tightly  in  a  barrel.  Since  barrels  of 
different  brands  vary  widely  in  size,  the  careful  engineer  or 
contractor  will  test  any  brand  he  intends  using  in  large  quan- 
tities, in  order  to  ascertain  exactly  how  much  cement  paste 
can  be  made.  He  will  find  a  range  of  from  3.2  cu.  ft.  to  3.8 
cu.  ft.  per  barrel  of  Portland  cement.  Obviously  the  larger 
barrel  may  be  cheaper  though  its  price  is  higher.  Specifica- 


36  CONCRETE    CONSTRUCTION. 

tions  often  state  the  number  of  cubic  feet  that  will  be  allowed 
per  barrel  in  mixing-  the  concrete  ingredients,  so  that  any  rule 
or  formula  to  be  of  practical  value  must  contain  a  factor 
to  allow  for  the  specified  size  of  the  barrel,  and  another  factor 
to  allow  for  the  actual  number  of  cubic  feet  of  paste  that  a 
barrel  will  yield— the  two  being  usually  quite  different. 

The  deduction  of  a  rational,  practical  formula  for  comput- 
ing the  quantity  of  cement  required  for  a  given  mixture  will 
now  be  given,  based  upon  the  facts  above  outlined. 

Let  p  =  number  of  cu.  ft.  cement  paste  per  bbl.,  as  deter- 
mined by  actual  test. 

n  =  number  of  cu.  ft.  of  cement  per  bbl.,  as  specified  in 
the  specifications. 

5  =  parts  of  sand  (by  volume)  to  one  part  of  cement,  as 
specified. 

g  =  parts  of  gravel  or  broken  stone  (by  volume)  to  one 
part  of  cement,  as  specified. 

v  =  percentage  of  voids  in  the  dry  sand,  as  determined 
by  test. 

V  =  percentage  of  voids  in  the  gravel  or  stone,  as  deter- 
mined by  test. 

Then,  in  a  mortar  of  1  part  cement  to  5  parts  sand,  we  have: 

;/  5  -  cu.  ft.  of  dry  sand  to  1  bbl.  of  cement. 
n  s  v  =          "   "    voids  in  the  dry  sand. 
0.9  n  s  v  =  '  ."    available  voids  in  the  wet  sand. 

1.1  n  s  =    "     "   "    wet  sand. 
p— 0.9ns v  =  "    cement  paste  in  excess  of  the  voids. 

Therefore: 
1.1  n  s  +  (p  —  0.9ns  v)  -  cu.  ft.  of  mortar  per  bbl. 

Therefore: 

27  27 

N  =* = 

1.1  ns  +  (p  —  0.9  n  s  v)         p  +  n  s  (1.1  —  0.9  v} 
N  being  the  number  of  barrels  of  cement  per  cu.  yd.  of  mortar. 
When  the  mortar  is  made  so  lean  that  there  is  not  enough 
cement  paste  to  fill  the  voids  in  the  sand,  the  formula  becomes: 

27 

N    =   ; 

1.1  ns 


PROPORTIONING   CONCRETE.  37 

A  similar  line  of  reasoning  will  give  us  a  rational  formula 
for  determining  the  quantity  of  cement  in  concrete ;  but  there 
is  one  point  of  difference  between  sand  and  gravel  (or  broken 
stone),  namely,  that  the  gravel  does  not  swell  materially  in 
volume  when  mixed  with  water.  However,  a  certain  amount 
of  water  is  required  to  wet  the  surface  of  the  pebbles,  and  this 
water  reduces  the  available  voids,  that  is,  the  voids  that  can 
be  filled  by  the  mortar.  With  this  in  mind,  the  following 
deduction  is  clear,  using  the  nomenclature  and  symbols  above 
given : 

ng  =  cu.  ft.  of  dry  gravel  (or  stone). 
ng  V  =   "     "    "   voids  in  dry  gravel. 
0.9  ng  V  =   "     "    "    "available  voids"  in  the  wet  gravel. 
p  +  ns  (1.1  —0.9  v)  —  0.9  ng  V -  excess  of  mortar  over  the  avail- 
able voids  in  the  wet  gravel. 

ng  +  p  +  ns  (1.1  —  0.9  v)  —  0.9  ng  V   =  cu.  ft.  of  concrete  from 
1  bbl.  cement. 


p  +  ns  (1.1  —  0.9v]  +  ng(l  -0.9V] 

N  being  the  number  of  barrels  of  cement  required  to  make 
I  cu.  yd.  of  concrete. 

This  formula  is  rational  and  perfectly  general.  Other  ex- 
perimenters may  find  it  desirable  to  use  constants  slightly 
different  from  the  i.i  and  the  0.9,  for  fine  sands  swell  more 
than  coarse  sands,  and  hold  more  water. 

The  reader  must  bear  in  mind  th.at  when  the  voids  in  the 
sand  exceed  the  cement  paste,  and  when  the  available  voids  in 
the  gravel  (or  stone)  exceed  the  mortar,  the  formula  becomes : 

27 
N  = 


ng 

These  formulas  give  the  amounts  of  cement  in  mortars  and 
concretes  compacted  in  place.  Tables  X  to  XIII  are  based 
upon  the  foregoing  theory,  and  will  be  found  to  check  satis- 
factorily with  actual  tests. 


CONCRETE    CONSTRUCTION. 


In    using    these 
cement  to  sand   is 
specifications  state 
ered  to  hold  4  cu. 
be   i   part  cement 

TABLE  X. — BARRK 


tables    remember   that    the    proportion    of 
by  volume,  and   not  by  weight.      If  the 
that  a  barrel  of  cement  shall  be  consid- 
ft.,  for  example,  and  that  the  mortar  shall 
to  2   parts  sand,   then    r    barrel   of  cement 

LS  OF  PORTLAND  CEMENT  PER  CUBIC  YARD  OF 
MORTAR. 


(Voids  in  sand  being  35%,  and  1  bbl.  cement  yielding  3.65  cu.  ft.  of 

cement  paste.) 


Proportion  of  Cement  to  Sand 

1  to  1 

1  to  1| 

1  to2 

1  to  2^ 

1  to  3 

1  to  4 

Bbls. 

Bbls. 

Bbls. 

Bbls. 

Bbls. 

Bbls. 

Barrel  specified  to  be  3.5  cu.ft. 
"      3.8     " 

4.22 
4.09 

3.49 
3.33 

2.97 
2.81 

2.57 
2.45 

2.28 
2.16 

1.76 
1.62 

"      4.0     " 

4.00 

3.24 

2.73 

2.36 

2.08 

1.54 

"      4.4     ' 

3.81 

3.07 

2.57 

2.27 

2.00 

1.40 

Cu. yds.  sand  per  cu. yd. mortar ;  0.6     j  0.7 


0. 


1.0 


is  mixed  with  8  cu.  ft.  of  sand,  regardless  of  what  is  the  actual 
size  of  the  barrel,  and  regardless  of  how  much  cement  paste 
can  be  made  with  a  barrel  of  cement.  If  the  specifications 
fail  to  state  what  the  size  of  a  barrel  will  be,  then  the  con- 
tractor is  left  to  guess. 

TABLE  XI. — BARRELS  OF  PORTLAND  CEMENT  PER  CUBIC  YARD  OF 

MORTAR. 

(Voids  in  sand  being  45%,  and   1  bbl.   cement  yielding  3.4  cu.   ft.  of 

cement  paste.) 


Proportion  of  Cement  to  Sand 

Ito  1 

1  to  li 

1  to  2 

1  to2| 

1  to  3 

1  to  4 

Barrel  specified  to  be  3.5  cu.ft. 
"      3.8     " 
"     4.0     " 
4.4 

Cu.yds.  sand  per  cu.yd.mortar 

Bbls. 
4.62 
4.32 
4.19 
3.94 

Bbls. 
3.80 
3.61 
3.46 
3.34 

Bbls. 
3.25 
3.10 
3.00 
2.90 

Bbls. 
2.84 
2.72 
2.64 
2.57 

Bbls. 
2.35 
2.16 
2.05 
1.86 

Bbls. 
1.76 
1.62 
1.54 

1.40 

0.6 

0.8 

0.9 

1.0 

1.0 

1.0 

If  the  specifications  call  for  proportions  by  weight,  assume 
a  Portland  barrel  to  contain  380  Ibs.  of  cement,  and  test  the 
actual  weight  of  a  cubic  foot  of  the  sand  to  be  used.  Sand 
varies  extremely  in  weight,  due  both  to  the  variation  in  the 
per  cent,  of  voids,  and  to  the  variation  in  the  kind  of  minerals 
of  which  the  sand  is  composed.  A  quartz  sand  having  35  per 
cent,  voids  weighs  107  Ibs.  per  cu.  ft. ;  but  a  quartz  sand 


PROPORTIONING   CONCRETE. 


39 


having  45  per  cent,  voids  weighs  only  91  Ibs.  per  cu.  ft.  If 
the  weight  of  the  sand  must  be  guessed  at,  assume  100  Ibs. 
per  cu.  ft.  If  the  specifications  require  a  mixture  of  i  cement 
to  2  of  sand  by  weight,  we  will  have  380  Ibs.  (or  I  bbl.) 
of  cement  mixed  with  2  X  380,  or  760  Ibs.  of  sand ;  and  if  the 
sand  weighs  90  Ibs.  per  cu.  ft.,  we  shall  have  760  ~-  90,  or  8.44 
cu.  ft.  of  sand  to  every  barrel  of  cement.  In  order  to  use  the 
tables  above  given,  we  may  specify  our  own  size  of  barrel ;  let 
us  say  4  cu.  ft.;  then  8.44-^-4  gives  2.11  parts  of  sand  by 
volume  to  I  part  of  cement.  Without  material  error  we  may 
call  this  a  i  to  2  mortar,  and  use  the  tables,  remembering  that 
our  barrel  is  now  "specified  to  be"  4  cu.  ft.  If  we  have  a 
brand  of  cement  that  yields  3.4  cu.  ft.  of  paste  per  bbl..  and 
sand  having  45  per.  cent,  voids,  we  find  that  approximately  3 
bbls.  of  cement  per  cu.  yd.  of  mortar  will  be  required. 

TABLE  XII. — INGREDIENTS  IN  1  CUBIC  YARD  OF  CONCRETE. 

(Sand  voids,  40% ;    stone  voids,  45% ;    Portland  cement  barrel  yielding 

3.65  cu.  ft.  paste.     Barrel  specified  to  be  3.8  cu.  ft. 


Proportions  by  Volume. 

1:2:4 

1:2:5 

1:2:6 

1:2^:5 

1:2^:6 

1  :3  A 

Bbls.  cement  per  cu.  yd.  concr't 
Cu.  yds.  sand 
Cu.  yds.  stone 

1.46 
0.41 
0.82 

1.30 
0.36 
0.90 

1.18 
0.33 
1.00 

1.13 
0.40 
0.80 

1  .  00 
0.35 
0.84 

1  .  15 
0.53 
0.71 

Proportions  by  Volume. 

1  :3  :5 

1:3:6 

1:3:7 

1:4:7 

1:4:8 

1:4:«.» 

Bbls.  cement  per  cu.  yd.  concr't 
Cu.  yds.  sand 
Cu.  yds.  stone 

1.13 
0.48 
0.80 

1.05 
0.44 
0.88 

0.96 
0.40 
0.93, 

0.82 
0.46 
0.80 

0.77 
0.43 
"0.86 

0.73 
0.41 
0.92 

NOTE.-— This  table  is  to  be  used  where  cement  is  measured  packed  in 
the  barrel,  for  the  ordinary  barrel  holds  3.8  cu.  ft. 

It  should  be  evident  from  the  foregoing  discussions  that  no 
table  can  be  made,  and  no  rule  can  be  formulated  that  will 
yield  accurate  results  unless  the  brand  of  cement  is  tested 
and  the  percentage  of  voids  in  the  sand  determined.  This 
being  so  the  sensible  plan  is  to  use  the  tables  merely  as  a 
rough  guide,  and,  where  the  quantity  of  cement  to  be  used  is 
very  large,  to  make  a  few  batches  of  mortar  using  the  avail- 
able brands  of  cement  and  sand  in  the  proportions  specified. 
Ten  dollars  spent  in  this  way  may  save  a  thousand,  even  on  a 
comparatively  small  job,  by  showing  what  cement  and  sand 
to  select.  « 


40 


CONCRETE    CONSTRUCTION. 


It  will  be  seen  that  Tables  XII  and  XIII  can  be  condensed 
into  the  following  rule : 

Add  together  the  number  of  parts  and  divide  this  sum  into 
ten.  the  quotient  will  be  approximately  the  number  of  barrels  of 
cement  per  cubic  yard. 

Thus  for  a  i  :2 :5  concrete,  the  sum  of  the  parts  is  i  4-  2  +  5, 
which  is  8;  then  io-=-8  is  1.25  bbls.,  which  is  approximately 
equal  to  the  1.30  bbls.  given  in  the  table.  Neither  is  this  rule 
nor  are  the  tables  applicable  if  a  different  size  of  cement  bar- 
rel is  specified,  or  if  the  voids  in  the  sand  or  stone  differ  ma- 

TABLE  XIII. — INGREDIENTS  IN  1  CUBIC  .YARD  OF  CONCRETE. 

(Sand  voids,  40%;    stone  voids,  45%;    Portland  cement  barrel  yielding 
3.65  cu.  ft.  of  paste.     Barrel  specified  to  be  4.4  cu.  ft.) 


Proportions  by  Volume. 

1:2:4 

1  :2  :5 

1:2:6 

1:2^:5 

1:2^:6 

1:3:4 

Bbls.  cement  per  cu.  yd.  concr't 
Cu.  yds.  sand 
Cu.  yds.  stone 

1.30 
0.42 
0.84 

1.16 
0.38 
0.95 

1.00 
0.33 
1.00 

1.07 
0.44 
0.88 

0.96 
0.40 
0.95 

1  .  08 
0.53 
0.71 

Proportions  by  Volume. 

1  :3  :5 

1:3:6 

1:3:7 

1:4:7 

1:4:8 

1  :4  :9 

Bbls.  cement  per  cu.  yd.  concr't 
Cu.  yds.  sand 
Cu.  yds.  stone 

0.96 
0.47 
0.78 

0.90 
0.44 
0.88 

0.82 
0.40 
0.93 

0.75 
0.49 
0.86 

0.68 
0.44 
0.88 

0.64 
0.42 
0  .  95 

NOTE. — This  table  is  to  be  used  when  the  cement  is  measured  loose, 
after  dumping  it  into  a  box,  for  under  such  conditions  a  barrel  of  cement 
yields  4.4  cu.  ft.  of  loose  cement. 

terially  from  40  per  cent,  to  45  per  cent,  respectively.  There 
are  such  innumerable  combinations  of  varying  voids,  and 
varying  sizes  of  barrel,  that  the  authors  do  not  deem  it  worth 
while  to  give  other  tables.  The  following  amounts  of  cement 
per  cubic  yard  of  mortar  were  determined  by  test: 


Authority 

Neat. 

1  to  1 

1  to  2 

Ito3 

1  to  4 

Ito5 

Ito6 

Ito7 

1  to  8 

Sabin  
W.  B.  Fuller.  .  .  . 
H.  P.  Board  man. 

Bbls. 
7.40 
8.02 
7.40 

Bbls. 
4.17 
4.58 
4.60 

Bbls. 
2.84 
3.09 
3  18 

Bbls. 
2.06 
2.30 
2  35 

Bbls. 
1.62 
1.80 

Bbls. 
1.33 
1.48 

Bbls. 
1.14 
1.23 

Bbls. 

'  'i.'iV  ' 

Bbls. 

'i!do  ' 

The  proportions  were  by  barrels  of  cement  to  barrels  of 
sand,  and  Sabin  called  a  38o-lb.  barrel  3.65  cu.  ft.,  whereas 
Fuller  called  a  38o-lb.  barrel  3.80  cu.  ft. ;  and  Boardman  called 


PROPORTIONING   CONCRETE. 


a  38o-lb.  oarrel  3.5  cu.  ft.  Sabin  used  a  sand  having  38  per 
cent,  voids ;  Fuller  used  a  sand  having  45  per  cent,  voids ;  and 
Boardman  used  a  sand  having  '38  per  cent,  voids.  It  will  be 
seen  that  the  cement  used  by  Sabin  yielded  3.65  cu.  ft.  of 
cement  paste  per  bbl.  (i.  e.  27-^-7.4),  whereas  the  (Atlas) 
cement  used  by  Fuller  yielded  3.4  cu.  ft.  of  cement  paste  per 
bbl.  Sabin  found  that  a  barrel  of  cement  measured  4.37  cu.  ft. 
when  dumped  and  measured  loose.  Mr.  Boardman  states  a 
barrel  (380  Ibs.,  net)  of  Lehigh  Portland  cement  yields  3.65 
cu.  ft.  of  cement  paste ;  and  that  a  barrel  (265  Ibs.,  net)  of 
Louisville  natural  cement  yields  3.0  cu.  ft.  of  cement  paste. 

Mr.  J.  J.  R.  Croes,  M.  Am.  Soc.  C.  E.,  states  that  I  bbl.  of 
Rosendale  cement  and  2  bbl.  of  sand  (8  cu.  ft.)  make  9.7  cu.  ft. 
of  mortar,  the  extreme  variations  from  this  average  being  7 
per  cent. 

Frequently  concrete  is  made  by  mixing  one  volume  of  ce- 
ment with  a  given  number  of  volumes  of  pit  gravel;  no  sand 
being  used  other  than  the  sand  that  is  found  naturally  mixed 
with  the  gravel.  In  such  cases  the  cement  rarely  increases 
the  bulk  of  the  gravel,  hence  Table  XIV  will  give  the  ap- 
proximate amount  of  cement,  assuming  I  cu.  yd.  of  gravel 
per  cubic  yard  of  concrete. 

TABLE    XIV. — SHOWING    BARRELS   OF   CEMENT    PER   CU;BIC    YARD    OF 
VARIOUS  MIXTURES  OF  CEMENT  AND  PIT  GRAVEL. 


Spc.Vol. 
of  bbl. 
cu.  ft. 

Barrels  of  Cement  per  Cubic  Yard  of  Concrete  for  Mixtures  of 

1-5 

1-6 

1-7 

1-8 

1-9 

1-10 

1-12 

3.8 
4.4 

1.41 
1.25 

1.18 
1.02 

1.01 
0.875 

0.874 
0.7G6 

0.789 
0.081 

0.71 
0.61 

0.59 
0.51 

PERCENTAGE    OF    WATER   IN    CONCRETE.— Tests 

show  that  dry  mixtures  when  carefully  deposited  and  well 
tamped  produce  the  stronger  concrete.  This  superiority  of 
dry  mixtures  it  must  be  observed  presupposes  careful  deposi- 
tion and  thorough  tamping,  and  these  are  tasks  which  are  dif- 
ficult to  have  accomplished  properly  in  actual  construction 
work  and  which,  if  accomplished  properly,  require  time  and 
labor.  Wet  mixtures  readily  flow  into  the  corners  and  angles 
of  the  forms  and  between  and  around  the  reinforcing  bars 
with  only  a  small  amount  of  puddling  and  slicing  and  are, 


42  CONCRETE    CONSTRUCTION. 

therefore,  nearly  always  used  because  of  the  time  and  labor 
saved  in  depositing  and  tamping.  The  following  rule  by 
which  to  determine  the  percentage  of  water  by  weight  for  any 
given  mixture  of  mortar  for  wet  concrete  will  be  found  satis- 
factory : 

*  Multiply  the  parts  of  sand  by  8,  add  24  to  the  product,  and 

divide  the  total  by  the  sum  of  the  parts  of  sand  and  cement. 

For  example  if  the  percentage  of  water  is  required  for  a  1-3 

(3  X  8)  +  24 
mortar:     =  12.     Hence  the  water  should  be  12 

4 

per  cent,  of  the  combined  weight  of  cement  and  sand.  For  a 
i-i  mortar  the  rule  gives  16  per  cent. ;  for  a  1-2  mortar  it  gives 
i$V2  per  cent.,  and  for  a  1-6  mortar  it  gives  10.3  per  cent. 

To  calculate  the  amount  of  water  per  cubic  yard  of  1-3-6 
concrete  for  example  the  procedure  would  be  as  follows :    By 

(3  X  8)  +  24 
the  above  rule  a  1-3  mortar  requires  =  12  per 

4 

cent,  water.  A  1-3-6  concrete,  according  to  Table  XII,  con- 
tains 1.05  bbls.  cement  and  0.44  cu.  yd.  sand.  Cement  weighs 
380  Ibs.  per  barrel,  hence  1.05  bbls.  would  weigh  380  X  1.05 
=  399  Ibs.  Sand  weighs  2,700  Ibs.  per  cu.  yd.,  hence  0.44  cu. 
yd.  of  sand  would  weigh  2,700  X  0.44=  1,188  Ibs.  The  com- 
bined weight  of  the  cement  and  sand  would  thus  be  399  -4- 
1,188=1,587  Ibs.  and  12  per  cent,  of  1,587  Ibs.  is  190  Ibs.  of 
water.  Water  weighs  8.355  Ibs.  per  gallon,  hence  190  X  8,355 
=  23  gallons  of  water  per  cubic  yard  of  1-3-6  concrete. 

METHODS  OF  MEASURING  AND  WEIGHING.— The 

cement,  sand  and  aggregate  for  concrete  mixtures  are  usually 
measured  by  hand,  the  measuring  being  done  either  in  the 
charging  buckets  or  in  the  barrows  or  other  receptacles  used 
to  handle  the  material  to  the  charging  buckets.*  The  process 
is  simple  in  either  case  when  once  the  units  of  measurement 
are  definitely  stated.  This  is  not  always  the  case.  Some  engi- 
neers require  the  contractor  to  measure  the  sand  and  stone  in 
the  same  sized  barrel  that  the  cement  comes  in,  in  which  case 
i  part  of  sand  or  aggregate  usually  means  3.5  cu.  ft.  Other 
engineers  permit  both  heads  of  the  barrel  to  be  knocked  out 


PROPORTIONING   CONCRETE.  43 

for  convenience  in  measuring  the  sand  and  stone,  in  which 
case  a  barrel  means  3.75  cu.  ft.  Still  other  engineers  permit 
the  cement  to  be  measured  loose  in  a  box,  then  a  barrel  usually 
means  from  4  to  4.5  cu.  ft.  Cement  is  shipped  either  in  barrels 
or  in  bags  and  the  engineer  should  specify  definitely  the  vol- 
ume at  which  he  will  allow  the  original  package  to  be  counted, 
and  also,  if  cement  barrels  are  to  be  used  in  measuring  the 
sand  and  stone,  he  should  specify  what  a  "barrel"  is  to  be. 
When  the  concrete  is  to  be  mixed  by  hand  the  better  practice 
is  to  measure  the  sand  and  stone  in  bottomless  boxes  of  the 
general  type  shown  by  Fig.  10  and  of  known  volume,  and  then 


Fig.  10. — Bottomless  Box  for  Measuring  Materials  in  Proportioning  Concrete. 

specify  that  a  bag  of  cement  shall  be  called  i  cu.  ft.,  0.6  cu.  ft., 
or  such  other  fraction  of  a  cubic  foot  as  the  engineer  may 
choose.  The  contractor  then  has  a  definite  basis  on  which  to 
estimate  the  quantity  of  cement  required  for  any  specified  mix- 
ture. The  same  is  true  if  the  measuring  of  the  sand  and  stone 
be  done  in  barrows  or  in  the  charging  bucket.  The  volume 
of  the  bag  or  barrel  of  cement  being  specified  the  contractor 
has  a  definite  and  simple  problem  to  solve  in  measuring  his 
materials. 

To  avoid  uncertainty  and  labor  in  measuring  the  cement, 
sand  and  stone  or  gravel  various  automatic  measuring  devices 
have  been  designed.  A  continuous  mixer  with  automatic 
measuring  and  charging  mechanism  is  described  in  Chapter 
XIV.  Figure  n  shows  the  Trump  automatic  measuring  de- 
vice. It  consists  of  a  series  of  revolving  cylinders,  each  open- 
ing onto  a  "table,"  which  revolves  with  the  cylinders,  and  of 
a  set  of  fixed  "knives,"  which,  as  the  "tables"  revolve,  scrape 
ofif  portions  of  the  material  discharged  from  each  cylinder 
onto  its  "table."  The  illustration  shows  a  set  of  two  cylinders; 
for  concrete  work  a  third  -cylinder  is  added.  The  three  tables 
are  set  one  above  the  other,  each  with  its  storage  cylinder,  and 
being  attached  to  the  same  spindle  all  revolve  together.  For 


44 


CONCRETE    CONSTRUCTION. 


each  table  there  is  a  knife  with  its  own  adjusting  mechanism. 
These  knives  may  be  adjusted  at  will  to  vary  the  percentage 
of  material  scraped  off. 

Automatic  measuring  devices  are  most  used  in  connection 


Fig.    11.— Sketch    Showing   Trump    Automatic    Measuring   Device    for    Mate- 
rials in  Proportioning  Concrete. 

with  continuous  mixers,  but  they  may  be  easily  adapted  to 
batch  mixers  if  desired.  One  point  to  be  observed  is  that  all 
of  these  automatic  devices  measure  the  cement  loose  and  this 
must  be  allowed  for  in  proportioning  the  mixture. 


CHAPTER  III. 

METHODS  AND  COST  OF  MAKING  AND  PLACING 
CONCRETE  BY  HAND. 

The  making  and  placing  of  concrete  by  hand  is  divided  into 
the  following  operations  :  (i)  Loading  the  barrows,  buckets,  , 
carts  or  cars  used  to  transport  the  cement,  sand  and  stone  to 
the  mixing  board;  (2)  Transporting  and  dumping  the  mate- 
rial; (3)  Mixing  the  material  by  turning  with  shovels  and 
hoes;  (4)  Loading  the  concrete  by  shovels  into  barrows, 
buckets,  carts  or  cars ;  (5)  Transporting  the  concrete  to  place; 
(6)  Dumping  and  spreading ;  (7)  Ramming. 

LOADING  INTO  STOCK  PILES.— Stock  piles  should  al- 
ways be  provided  unless  there  is  some  very  good  reason  to 
the  contrary.  They  prevent  stoppage  of  work  through  irreg- 
ularities in  the  delivery  of  the  material,  and  they  save  fore- 
man's time  in  watching  that  the  material  is  delivered  as 
promptly  as  needed  for  the  work  immediately  in  hand.  The 
location  of  the  stock  piles  should  be  as  close  to  the  work  as 
possible  without  being  in  the  way  of  construction  ;  forethought 
both  in  locating  the  piles  and  in  proportioning  their  size  to  the 
work  will  save  the  contractor  money. 

The  stone  and  sand  will  ordinarily  be  delivered  in  wagons 
or  cars.  If  delivered  in  cars,  effort  should  be  made  to  secure 
delivery  in  flat  cars  when  the  unloading  is  to  be  done  by 
shoveling;  this  is  more  particularly  necessary  for  the  broken 
stone.  Stone  can  be  shoveled  from  hopper  bottom  cars  only 
with  difficulty  as  compared  with  shoveling  from  flat  bottom 
cars;  the  ratio  is  about  14  cu.  yds.  per  day  per  man  from 
hopper  bottom  cars  as  compared  with  20  cu.  yds.  per  day  -per 
man  from  flat  bottom  cars.  When  the  cars  cr.n  be  unloaded 
through  a  trestle,  hopper  bottom  cars  should  by  all  means  be 
secured  for  delivering  the  stone.  If  the  amount  of  work  will 
justify  the  expense,  a  trestle  may  be  built ;  often  there  is  a 
railway  embankment  which  can  be  dug  away  for  a  short  dis- 

45 


46  CONCRETE    CONSTRUCTION. 

tance  and  the  track  carried  on  stringers  to  make  a  dumping 
place,  from  which  the  stone  can  be  shoveled. 

Sand  can  be  dumped  directly  on  the  ground,  but  broken 
stone  unless  it  is  very  small,  ^J-in.  or  less,  should  always  be 
dumped  on  a  well  made  plank  floor.  A  good  floor  is  made  of 
2-in.  plank,  nailed  to  4x6-in.  mud  sills,  spaced  3  ft.  apart,  and 
well  bedded  in  the  ground.  Loose  plank  laid  directly  on  the 
ground  settle  unevenly  and  thus  the  smooth  shoveling  surface 
which  is  sought  is  not  obtained;  the  object  of  the  floor  is  to 
provide  an  even  surface,  along  which  a  square  pointed  shovel 
can  be  pushed;  it  is  very  difficult  to  force  such  a  shovel  into 
broken  stone  unless  it  is  very  fine.  A  spading  fork  is  a  better 
tool  than  a  shovel,  with  which  to  load  broken  stone  from  piles. 
A  man  can  load  from  18  to  20  cu.  yds.  of  broken  stone  into 
wheelbarrows  or  carts  in  10  hours  when  shoveling  from  a  good 
floor,  but  he  can  load  only  12  to  14  cu.  yds.  per  day  when 
shoveling  from  a  pile  without  such  a  floor.  It  is  a  common 
thing  to  see  stone  unloaded  from  cars  directly  onto  the  sloping 
side  of  a  railway  embankment.  This  makes  very  difficult 
shoveling  and  results  in  a  waste  of  stone.  Stone  can  usually 
be  delivered  by  a  steel  lined  chute  directly  to  a  flooring  located 
at  the  foot  of  the  embankment ;  coarse  broken  stone  if  given 
a  start  when  cast  from  a  shovel  will  slide  on  an  iron  chute 
having  a  slope  as  flat  as  3  or  4  to  i  ;  sand  will  not  slide  on  a 
slope  of  I j/2  to  i.  When  chuting  is  not  practicable  it  will  pay 
often  to  shovel  the  stone  into  buckets  handled  by  a  stiff-leg 
derrick  rather  than  to  unload  it  onto  the  bank.  Stock  piles  of 
ample  storage  capacity  are  essential  when  delivery  is  by  rail, 
because  of  the  uncertainty  of  rail  shipments.  When  the  con- 
tractor is  taking  the  sand  and  stone  direct  from  pit  and  quarry 
by  wagon  it  is  not  necessary  to  have  large  stock  piles. 

LOADING  FROM  STOCK  PILES.— In  loading  sand  into 
wheelbarrows  or  carts  with  shovels  a  man  will  load  20  cu.  yds. 
per  lo-hour  day  if  he  is  energetic  and  is  working  under  a  good 
foreman.  Under  opposite  conditions  15  cu.  yds.  per  man  per 
day  is  all  that  it  is  safe  to  count  on.  A  man  shoveling  from 
a  good  floor  will  load  20  cu.  yds.  of  stone  per  lo-hour  day ; 
this  is  reduced  to  15  cu.  yds.  per  day  if  the  stone  is  shoveled 
off  the  ground  and  to  12  cu.  yds.  per  day  if  in  addition  the 


HAND   MIXING. 


47 


management  is  poor.  There  are  ordinarily  in  a  cubic  yard  of 
concrete  about  i  cu.  yd.  of  stone  and  0.4  cu.  yd.  of  sand,  so 
that  the  cost  of  loading  the  materials  into  barrows  or  carts, 
with  wages  at  15  cts.  per  hour  and  assuming  15  cu.  yds.  to  be 
a  day's  work,  would  be : 

i     cu  yd.  stone  loaded  for IO  cts. 

04  cu.  yd.  sand  loaded  for . . . 4  cts. 


Total    14  cts. 

To  this  is  to  be  added  the  cost  of  loading  the  cement.  This 
will  cost  not  over  2  cts.  per  cu.  yd.  of  concrete :  the  total  cost 
of  loading  concrete  materials  into  barrows  or  carts,  therefore, 
does  not  often  exceed  16  cts.  per  cu.  yd.  of  concrete. 

TRANSPORTING  MATERIALS  TO  MIXING  BOARDS 

— Carrying  the  sand  and  stone  from  stock  piles  to  mixing 
board  in  shovels  should  never  be  practiced.  It  takes  from 
100  to  150  shovelfuls  of  stone  to  make  i  cu.  yd.;  it,  therefore, 
costs  50  cts.  per  cu.  yd.  to  carry  it  100  ft.  and  return  empty 
handed,  for  in  walking  short  distances  the  men  travel  very 
slowly — about  150  ft.  per  minute.  It  costs  more  to  walk  a  half 
dozen  paces  with  stone  carried  in  shovels  than  to  wheel  it  hi 
barrows. 

The  most  common  method  of  transporting  materials  from 
stock  piles  to  mixing  boards  is  in  wheelbarrows.  The  usual 
wheelbarrow  load  on  a  level  plank  runway  is  3  bags  of  ce- 
ment (300  Ibs)  or  3  cu.  ft.  of  sand  or  stone.  If  a  steep  rise 
must  be  overcome  to  reach  the  mixing  platform  the  load  will 
be  reduced  to  2  bags  (200  Ibs.)  of  cement  or  2  cu.  ft.  of  sand 
or  stone.  A  man  wheeling  a  barrow  travels  at  a  rate  of  200  ft. 
per  minute,  going  and  coming,  and  loses  £4  minute  each  trip 
dumping  the  load,  fixing  run  planks,  etc.  An  active  man  will 
do  20  to  25  per  cent,  more  work  than  this,  while  a  very  lazy 
man  may  do  20  per  cent.  less.  With  wages  at  15  cts.  per  hour, 
the  cost  of  wheeling  materials  for  I  cu.  yd.  of  concrete  may  be 
obtained  by  the  following  rule: 

To  a  -fi.i-ed  cost  of  4  cts.  (for  lost  time)  aJd  i  ct.  for  every 
20  ft.  of  distance  away  from  the  stock  />//r  if  there  is  a  steep  rise 
in  the  runway,  but  if  the  runway  is  level,  add  I  ct.  for  every  jo 
ft.  distance  of  haul. 


OF  THE 

•NIVER31TY 


48  CONCRETE    CONSTRUCTION. 

Since  loading  the  barrqws,  as  given  above,  was  16  cts.  per 
cu.  yd.,  the  total  fixed  cost  is  16  +  4  —  2®  cts.  per  cu.  yd.,  to 
which  is  added  i  ct.  for  every  20  or  30  ft.  haul  depending  on 
the  grade  of  the  runway. 

The  preceding  figures  assume  the  use  of  plank  runways  for 
the  wheelbarrows.  These  should  never  be  omitted,  and  the 
barrows  wheeled  over  the  ground.  Even  a  hard  packed 
earth  path  in  dry  weather  is  inferior  to  a  plank  runway  and 
when  the  ground  is  soft  or  muddy  the  loss  in  efficiency  of  the 
men  is  serious.  Where  the  runway  must  rise  to  the  mixing 
board,  give  it  a  slope  or  grade  seldom  steeper  than  i  in  8,  and 
if  possible  flatter.  Make  a  runway  on  a  trestle  at  least  18  ins. 
wide,  so  that  men  will  be  in  no  danger  of  falling.  See  to  it, 
also,  that  the  planks  are  so  well  supported  that  they  do  not 
spring  down  when  walked  over,  for  a  springy  plank  makes 
hard  wheeling.  If  the  planks  are  so  long  between  the  "horses" 
or  "bents"  used  to  support  them,  that  they  spring  badly,  it  is 
usually  a  simple  matter  to  nail  a  cleat  across  the  underside  of 
the  planks  and  stand  an  upright  strut  underneath  to  support 
and  stiffen  the  plank. 

When  two-wheeled  carts  of  the  type  shown  by  Fig.  12  are 
used  the  runway  requires  two  lines  of  planks. 

Two-wheeled  carts  pushed  by  hand  have  been  less  used  for 
handling-  concrete  materials  than  for  handling  concrete,  but 
for  distances  from  50  to  150  ft.  from  stock  pile  to  mixing  board 
such  carts  are  probably  cheaper  for  transporting  materials 
than  are  wheelbarrows.  These  carts  hold  generally  three 
wheelbarrow  loads  and  they  are  handled  by  one  man  prac- 
tically as  rapidly  and  easily  as  is  a  wheelbarrow. 

For  all  distances  over  50  ft.  from  stock  pile  to  mixing  board, 
it  is  cheaper  to  haul  materials  in  one-horse  dump  carts  than  it 
is  in  wheelbarrows.  A  cart  should  be  loaded  in  4  minutes  and 
dumped  in  about  i  minute,  making  5  minutes  lost  time  each 
round  trip.  It  should  travel  at  a  speed  of  not  less  than  200 
ft.  per  minute,  although  it  is  not  unusual  to  see  variations  of 
15  or  20  per  cent.,  one  way  or  another,  from  this  average,  de- 
pending upon  the  management  of  the  work.  A  one-horse  cart 
will  readily  carry  enough  stone  and  sand  to  make  y2  cu.  yd.  of 
concrete,  if  the  roads  are  fairly  hard  and  level;  and  a  horse 


HAND    MIXIXG.  49 

can  pull  this  load  up  a  10  per  cent,  (rise  of  i  ft.  in  10  ft.) 
planked  roadway  provided  with  cleats  to  give  a  foothold.  If 
a  horse,  cart  and  driver  can  be  hired  for  30  cts.  per  hour,  the 
cost  of  hauling-  the  materials  for  i  cu.  yd.  of  concrete  is  given 
by  the  following  rule : 

To  a  fixed  cost  of  5  cts.  (for  lost  time  at  both  ends  of  haul) 
add  i  ct.  for  every  100  ft.  of  distance  from  stock  pile  to  miring 
board. 

Where  carts  are  used  it  is  possible  to  locate  the  stock  piles 
several  hundred  feet  from  the  mixing  boards  without  adding 


Fig.  12.— Two-Wheeled  Ransome    Cart  for  Hauling  Concrete. 

materially  to  the  cost  of  the  concrete.  It  is  well,  however,  to 
have  the  stock  piles  in  sight  of  the  foreman  at  the  mixing 
board,  so  as  to  insure  promptness  of  delivery. 

METHODS  AND  COST  OF*  MIXING.— In  mixing  con- 
crete by  hand  the  materials  are  spread  in  superimposed  lay- 
ers on  a  mixing  board  and  mixed  together  first  dry  and  then 
with  water  by  turning  them  with  shovels  or  hoes.  The  num- 
ber of  turns,  the  relative  arrangement  of  the  layers,  and  the 
sequence  of  operations  vary  in  practice  with  the  notions  of 


50  CONCRETE    CONSTRUCTION. 

the  engineer  controlling  the  work.  No  one  mode  of  pro- 
cedure in  hand  mixing  can,  therefore,  be  specified  for  general 
application ;  the  following  are  representative  examples  of  prac- 
tice in  hand  mixing : 

Measure  the  stone  in  a  bottomless  box  and  spread  it  until 
its  thickness  in  inches  equals  its  parts  by  volume.  Measure 
the  sand  in  a  bottomless  box  set  on  the  stone  and  spread  the 
sand  evenly  over  the  stone  layer.  Place  the  cement  on  the 
sand  and  spread  evenly.  Turn  the  material  twice  with  a 
square  pointed  shovel  and  then  turn  it  a  third  time  while 
water  is  gently  sprinkled  on.  A  fourth  turn  is  made  to  mix 
thoroughly  the  water  and  the  concrete  is  then  shoveled  into 
barrows,  giving  it  a  fifth  turn.  Mr.  Ernest  McCullough,  who 
gives  this  method,  states  that  it  is  the  cheapest  way  to  mix 
concrete  by  hand  and  still  secure  a  good  quality  of  output. 

In  work  done  by  Mr.  H.  P.  Boardman  the  sand  is  meas- 
ured in  a  bottomless  box  and  over  it  is  spread  the  cement  in 
an  even  layer.  The  cement  and  sand  are  mixed  dry  with  hoes, 
the  water  is  added  in  pailfuls  and  the  whole  mixed  to  a  uni- 
form porridge-like  consistency.  Into  this  thin  mortar  all  the 
stone  for  a  batch  is  dumped,  the  measuring  box  is  lifted  and 
the  mixture  turned  by  shovels.  A  pair  of  shovelers,  one  on 
each  side,  is  started  at  one  end  turning  the  material  back  and 
working  toward  the  opposite  end.  A  second  pair  of  shovelers 
takes  the  turned  material  and  turns  it  again.  The  concrete  is 
then  shoveled  into  the  barrows  by  the  wheelers  themselves  as 
fast  as  it  is  turned  the  second  time.  By  this  method  a  good 
gang  of  20  to  25  men,  using  two  boxes,  will,  Mr.  Boardman 
states,  mix  and  place  45  to  60  cu.  yds.  of  concrete  in  10  hours, 
depending  on  the  wheelbarrow  travel  necessary.  Assuming 
a  gang  of  25  men,  this  is  a  rate  of  1.8  to  2.4  cu.  yds.  per  man 
per  lohour  day,  concrete  mixed  and  placed. 

A  method  somewhat  similar  to  the  one  just  outlined  is  given 
by  Mr.  O.  K.  Morgan.  A  mixing  board  made  of  %-in. 
matched  boards  nailed  to  2x3~in.  sills  is  used,  with  a  mixing 
box  about  8  ft.  long,  4  ft.  wide  and  10  to  12  ins.  deep.  This 
box  is  set  alongside  the  mixing  board  and  in  it  the  cement 
and  sand  are  mixed  first  dry  and  then  wet ;  a  fairly  wet  mortar 
is  made.  Meanwhile  the  stone  is  spread  in  an  even  layer  6  ins. 


HAXD    M1XIXG.  5I 

thick  on  the  mixing-  board  and  thoroughly  drenched  with 
water.  The  mortar  from  the  mixing  box  is  cast  by  shovels  in 
a  fairly  even  layer  over  the  stone  and  the  whole  is  turned  two 
or  three  times  with  shovels,  generally  two  turns  are  enough. 
Six  men  are  employed ;  two  prepare  the  mortar,  while  four 
get  the  stone  in  readiness,  then  all  hands  finish  the  operation. 
The  following  method  is  given  by  Mr.  E.  Sherman  Gould: 
Spread  the  sand  in  a  thin  layer  on  the  mixing  board  and  over 
it  spread  the  cement.  Mix  dry  with  shovels,  using  four  men, 
one  at  each  corner,  turning  outward  and  then  working  back 
again.  Over  the  dry  sand  and  cement  mixture  spread  the 
broken  stone  which  has  been  previously  wetted  and  on  top  of 
the  stone  apply  water  evenly.  The  water  will  thus  percolate 
through  the  stone  without  splashing  and  evenly  wet  the  sand 
and  cement.  Finally  turn  the  whole,  using  the  same  number 
of  men  and  the  same  mode  of  procedure  as  were  used  in  dry 
mixing  the  sand  and  cement.  Mr.  Gould  states  that  by  this 
method  the  contractor  should  average  2  cu.  yds.  of  mixed  con- 
crete per  man  per  lo-hour  day. 

A  novel  method  of  hand  mixing  and  an  unusual  record  of 
output  is  described  by  Maj.  H.  M.  Chittenden,  U.  S.  A.,  in 
connection  with  the  construction  of  a  concrete  arch  bridge. 
The  mixing  was  done  by  hand  on  a  single  board  25  ft.  long 
and  sloping  slightly  from  one  end  to- the  other.  The  materials 
were  dumped  together  on  the  upper  end  of  the  board.  Sixteen 
men  were  stationed  along  the  board,  eight  on  each  side.  The 
first  two  men  turned  the  mixture  dry.  Next  to  them  stood  a 
man  who  applied  the  water  after  each  shovelful.  The  next 
mixers  kept  turning  the  material  along  and  another  waterman 
assisted  in  wetting  it  further  down  the  board.  The  men  at 
the  end  of  the  board  shoveled  the  concrete  into  the  carts  which 
took  it  to  the  work.  Each  batch  contained  18  cu.  ft.,  or  0.644 
cu.  yd.,  and  the  rate  of  mixing  was  10  cu.  yds.  per  hour,  or 
6.25  cu.  yds.  per  man  per  lo-hour  day.  The  work  of  getting 
the  materials  properly  proportioned  to  the  mixing  board  is,  not 
included  in  this  figure,  but  the  loading  of  the  mixed  concrete  is 
included. 

It  is  plain  from  the  foregoing,  that  specifications  for  hand 
mixing  should  always  state  the  method  to  be  followed,  and 


52  CONCRETE    CONSTRUCTION. 

particularly  the  number  of  turns  necessary.  If  these  matters 
are  not  specified  the  contractor  has  to  guess  at  the  probable 
requirements  of  the  engineer.  The  authors  have  known  of 
inspectors  demanding  from  6  to  9  turns  of  the  materials  when 
specifications  were  ambiguous.  It  should  also  be  made  clear 
whether  or  not  the  final  shoveling  into  the  barrows  or  carts 
constitutes  a  turn,  and  whether  any  subsequent  shoveling  of 
the  concrete  into  place  constitutes  a  turn.  Inspectors  and 
foremen  have  frequent  disputes  over  these  questions. 

Estimates  of  the  cost  of  hand  mixing  may  usually  be  figured 
upon  the  number  of  times  that  the  materials  are  to  be  turned 
by  shovels.  A  contractor  is  seldom  required  to  turn  the  sand 
and  cement  more  than  three  times  dry  and  three  times  wet, 
and  then  turn  the^mortar  and  stone  three  times.  A  willing 
workman,  under  a  good  foreman,  will  turn  over  mortar  at  the 
rate  of  30  cu.  yds.  in  10  hours,  lifting  each  shovelful  and  cast- 
ing it  into  a  pile.  With  wages  at  $1.50  and  six  turns,  this 
means  a  cost  of  5  cts.  per  cubic  yard  of  mortar  for  each  turn ; 
as  there  is  seldom  more  than  0.4  cu.  yd.  of  mortar  in  a  cubic 
yard  of  concrete,  we  have  a  cost  of  2  cts.  per  cubic  yard  of 
concrete  for  each  turn  that  is  given  the  moctar.  So  if  the 
mortar  is  given  six  turns  before  the  stone  is  added  and  then 
the  stone  and  mortar  are  mixed  by  three  turns  we  have : 
(2  cts.  X  6)  +  (5  cts.  X  3)  =  12  -f-  15  =  27  cts.  per  cubic  yard 
for  mixing  concrete.  In  pavement  foundation  work  two  turns 
of  the  mortar  followed  by  two  turns  of  the  mortar  and  stone 
are  considered  sufficient.  The  cost  of  mixing  per  cubic  yard 
of  concrete  is  then  (2  cts.  X  2)  +  (5  cts.  X  2)  =  4  -f-  10  =  14 
cts.  per  cubic  yard  of  concrete.  One  specification  known  to 
the  authors,  requires  six  turns  dry  and  three  turns  wet  for  the 
mortar ;  under  such  specifications  the  cost  of  mixing  the  mor- 
tar would  be  50  per  cent,  higher  than  in  the  first  example  as- 
sumed. On  the  other  hand,  they  have  seen  concrete  mixed 
for  street  pavement  foundation  with  only  three  turns  before 
shoveling  it  into  place.  These  costs  of  mixing  apply  to  v/ork 
done  by  diligent  men ;  easy  going  men  will  make  the  cost  25 
to  50  per  cent  greater. 

LOADING    AND    HAULING    MIXED    CONCRETE.— 
Wheelbarrows  and  carts  are  employed  to  haul  the  mixed  con- 


HAND  MIXING. 


53 


Crete  to  the  work.  The  loading  of  these  with  mixed  concrete 
by  shoveling  costs  less  than  the  loading  of  the  materials  sep- 
arately before  mixing.  While  the  weight  is  greater  because 
of  the  added  water  the  volume  of  the  concrete  is  much  less 
than  that  of  the  ingredients  before  mixing.  Again  the  shovel- 
ing is  done  off  a  smooth  board  with  the  added  advantage  of 
having  the  material  lubricated  and,  finally,  the  foreman  is 
usually  at  this  point  to  crowd  the  work.  A  good  worker  will 
load  12^/2  cu.  yds.  of  concrete  per  lo-hour  day,  and  with  wages 
at  $1.50  per  day  this  would  give  a  cost  of  12  cts.  per  cu.  yd. 
for  loading. 

Practically  the  same  principles  govern  the  transporting  of 
concrete  in  barrows  as  govern  the  handling  of  the  raw  mate- 
rials in  them.  The  cost  of  wheeling  concrete  is  practically  the 
same  as  for  wheeling  the  dry  ingredients,  so  that  the  total 
cost  of  loading  and  wheeling  may  be  estimated  by  the  fol- 
lowing rule : 

To  a  fixed  cost  of  16  cts.  for  loading  and  lost  time  add  I  ct. 
for  every  jo  ft.  of  level  haul. 

Within  a  few  years  wheelbarrows  have  been  supplanted  to  a 
considerable  extent  by  hand  carts  of  the  general  type  shown 
by  Fig.'  12,  which  illustrates  one  made  by  the  Ransome 
Concrete  Machinery  Co.  The  bowl  of  this  cart  has  a  capacity 
of  6  cu.  ft.  water  measure.  It  is  hung  on  a  i^-in.  steel  axle; 
the  wheels  are  42  ins,  in  diameter  with  staggered  spokes  and 
2-in.  half  oval  tires.  The  top  of  the  bowl  is  29^  ins.  from  the 
ground.  Owing  to  the  large  diameter  of  the  wheels  and  the 
fact  that  no  weight  comes  on  the  wheeler,  as  with  a  wheel- 
barrow, this  cart  is  handled  by  one  man  about  as  rapidly  and 
easily  as  is  a  wheeelbarrow.  It  will  be  noted  that  the  two 
ends  of  the  bowl  differ  in  shape;  the  handle  is  removable  and 
can  bt  attached  to  either  end  of  the  bowl.  With  the  handle 
attached  as  shown  the  bowl  can  be  inverted  for  discharging 
onto  a  pavement  or  floor;  with  the  handle  transferred  to  the 
opposite  end  the  bowl  is  fitted  for  dumping  into  narrow  beam 
or  wall  forms.  The  maximum  load  of  wet  concrete  for  a 
wheelbarrow  is  2  cu.  ft.,  and  this  is  a  heavy  load  and  one  that 
is  seldom  averaged — I  to  il/2  cu.  ft.  is  more  nearly  the  general 
average.  A  cart  of  the  above  type  will,  therefore,  carry  from 


54 


CONCRETE    CONSTRUCTION. 


3  to  5  wheelbarrow  loads,  and  on  good  runways,  which  are 
essential,  may  be  pushed  and  dumped  about  as  rapidly  as  a 
wheelbarrow.  In  succeeding-  pages  are  given  records  of  actual 
work  with  hand  carts  which  should  be  studied  in  this  connec- 
tion. 

Portland  cement  concrete  can  be  hauled  a  considerable  dis- 
tance in  a  dump  cart  or  wagon  before  it  begins  to  harden ; 
natural  cement  sets  too  quickly  to  permit  of  its  being  hauled 
far.  Portland  cement  does  not  begin  to  set  in  less  than  30 
minutes.  On  a  good  road,  with  no  long,  steep  hills  a  team 
will  haul  a  loaded  wagon  at  a  speed  of  about  200  ft.  per  min- 
ute ;  it,  therefore,  takes  6l/2  minutes  to  travel  a  quarter  of  a 
mile,  13  minutes  to  travel  half  a  mile,  and  26  minutes  to 
travel  a  mile.  Portland  cement  concrete  can,  therefore,  be 
hauled  a  mile  before  it  begins  to  set.  The  cost  of  hauling  con- 
crete in  carts  is  about  the  same  as  the  cost  of  hauling  the  raw 
materials  as  given  in  a  preceding  section. 

When  hand  mixing  is  employed  in  building  piers,  abut- 
ments, walls,  etc.,  the  concrete  often  has  to  be  hoisted  as  well 
as  wheeled.  A  gallows  frame  or  a  mast  with  a  pulley  block  at 
the  top  and  a  team  of  horses  can  often  be  used  in  such  cases 
as  described  in  Chapter  XII  for  filling  cylinder  piers,  *or  in  the 
same  chapter  for  constructing  a  bridge  abutment.  It  is  also 
possible  often  to  locate  the  mixing  board  on  high  ground,  per- 
haps at  some  little  distance  from  the  forms.  If  this  can  be 
done,  the  use  of  derricks  may  be  avoided  as  above  suggested 
or  by  building  a  light  pole  trestle  from  the  mixing  board  to 
the  forms.  The  concrete,  can  then  be  wheeled  in  barrows 
and  dumped  into  the  forms.  If  the  mixing  board  can  be  lo- 
cated on  ground  as  high  as  the  top  of  the  concrete  structure 
is  to  be,  obviously  a  trestle  will  enable  the  men  to  wheel  on 
a  level  runway.  Such  a  trestle  can  be  built  very  cheaply, 
especially  where  second-hand  lumber,  or  lumber  that  can  be 
used  subsequently  for  forms  is  available.  A  pole  trestle  whose 
bents  are  made  entirely  of  round  sticks  cut  from  the  forest  is 
a  very  cheap  structure,  if  a  foreman  knows  how  to  throw  it 
together  and  up-end  the  bents  after  they  are  made.  One  of 
the  authors  has  put  up  such  trestles  for  25  cts.  per  lineal  foot 
of  trestle,  including  all  labor  of  cutting  the  round  timber, 


IIASD   MIXING.  55 

erecting  it,  and  placing  a  plank  flooring  4  ft.  wide  on  top.  The 
stringers  and  flooring  plank  were  used  later  for  forms,  and 
their  cost  is  not  included.  A  trestle  100  ft.  long  can  thus  be 
built  at  less  cost  than  hauling,  erecting  and  taking  down  a 
derrick ;  and  once  the  trestle  is  up  it  saves  the  cost  of  oper- 
ating a  derrick. 

In  conclusion,  it  should  be  remarked  that  the  comparative 
economy  for  concrete  work  of  the  different  methods  of  haul- 
age described,  does  not  depend  wholly  on  the  comparative 
transportation  costs ;  the  effect  of  the  method  of  haulage  on 
•  the  cost  of  dumping  and  spreading  costs  must  be  considered. 
For  example,  if  carts  deliver  the  material  in  such  form  that 
the  cost  of  spreading  is  greatly  increased  over  what  it  would 
be  were  the  concrete  delivered  in  wheelbarrows,  the  gain  made 
by  cart  haulage  may  be  easily  wiped  out  or  even  turned  into 
loss  by  the  extra  spreading  charges.  These  matters  are  con- 
sidered more  at  length  in  the  succeeding  section. 

DUMPING,  SPREADING  AND  RAMMING.— The  cost 
of  dumping  wheelbarrows  and  carts  is  included  in  the  rules 
of  cost  already  given,  excepting  that  in  some  cases  it  is  neces- 
sary to  add  the  wages  of  a  man  at  the  dump  who  assists  the 
cart  drivers  or  the  barrow  men.  Thus  in  dumping  concrete 
from  barrows  into  a  deep  trench  or  pit,  it  is  usually  advisable 
to  dump  into  a  galvanized  iron  hopper  provided  with  an  iron 
pipe  chute.  One  man  can  readily  dump  all  the  barrows  that 
can  be  filled  from  a  concrete  mixer  in  a  day,  say  150  cu.  yds. 
At  this  rate  of  output  the  cost  of  dumping  would  be  only  I  ct. 
per  cu.  yd.,  but  if  one  man  were  required  to  dump  the  output 
of  a  small  gang  of  men,  say  25  cu.  yds.,  the  cost  of  dumping 
would  be  6  cts.  per  cu.  yd. 

Concrete  dumped  through  a  chute  requires  very  little  work 
to  spread  it  in  6-in.  layers ;  and,  in  fact,  concrete  that  can  be 
dumped  from  wheelbarrows,  which  do  not  all  dump  in  one 
place,  can  be  spread  very  cheaply ;  for  not  more  than  half  the 
pile  dumped  from  the  barrow  needs  to  be  moved,  and  then 
moved  merely  by  pushing  with  a  shovel.  Since  the  spreader 
also  rams  the  concrete,  it  is  difficult  to  separate  these  two 
items.  As  nearly  as  the  authors  have  been  able  to  estimate 
this  item  of  spreading  "dry"  concrete  dumped  from  wheel- 


56  CONCRETE    CONSTRUCTION. 

barrows  in  street  paving  work,  the  cost  is  5  cts.  per  cvt.  yd. 
If,  on  the  other  hand,  nearly  all  the  concrete  must  be  handled 
by  the  spreaders,  as  in  spreading  concrete  dumped  from  carts, 
the  cost  is  fully  double,  or  10  cts.  per  cu.  yd.  And  if  the 
spreader  has  to  walk  even  3  or  4  paces  to  place  the  concrete, 
after  shoveling  it  up,  the  cost  of  spreading  will  be  15  cts.  per 
cu.  yd.  For  this  reason  it  is  apparent  that  carts  are  not  as 
economical  as  wheelbarrows  for  hauling  concrete  up  to  about 
200  ft.,  due  to  the  added  cost  of  spreading  material  delivered 
by  carts. 

The  preceding  discussion  of  spreading  is  based  upon  the 
assumption  that  the  concrete  is  not  so  wet  that  it  will  run. 
Obviously  where  concrete  is  made  of  small  stones  and  con- 
tains an  excess  of  water,  it  will  run  so  readily  as  to  require 
little  or  no  spreading. 

The  cost  of  ramming  concrete  depends  almost  entirely  upon 
its  dryness  and  upon  the  number  of  cubic  yards  delivered  to 
the  rammers.  Concrete  that  is  mixed  with  very  little  water 
requires  long  and  hard  ramming  to  flush  the  water  to  the 
surface.  The  yardage  delivered  to  the  rammers  is  another 
factor,  because  if  only  a  few  men  are  engaged  in  mixing  they 
will  not  be  able  to  deliver  enough  concrete  to  keep  the  ram- 
mers properly  busy,  yet  the  rammers  by  slow  though  con- 
tinuous pounding  may  be  keeping  up  an  appearance  of  work- 
ing. Then,  again,  it  has  been  noticed  that  the  slower  the  con- 
crete 'is  delivered  the  more  particular  the  average  inspector 
becomes.  Concrete  made  "sloppy"  requires  no  ramming  at 
all,  and  very  little  spading.  The  authors  have  had  men  do 
very  thorough  ramming  of  moderately  dry  concrete  for  15  cts. 
per  cu>  yd.,  where  the  rammers  had  no  spreading  to  do,  the 
material  being  delivered  in  shovels.  It  is  rare  indeed  that 
spreading  and  ramming  can  be  made  to  cost  more  than  40  cts. 
per  cu.  yd.,  under  the  most  foolish  inspection,  yet  one  in- 
stance is  recorded  which,  because  of  its  rarity,  is  worth  noting: 
Mr.  Herman  Conrow  is  the  authority  for  the  data :  i  foreman, 
9  men  mixing,  i  ramming,  averaged  15  cu.  yds.  a  day,  or  only 
il/2  cu.  yds.  per  man  per  day,  when  laying  wet  concrete.  When 
laying  dry  concrete  the  same  gang  averaged  only  8  cu.  yds.  a 
day,  there  being  4  men  ramming.  With  foreman  at  $2  and 
laborers  at  $1.50  a  day,  the  cost  was  $2.12  per  cu.  yd.  for  labor 


HAND   MIXING. 


57 


on  the  dry  concrete  as  against  $1.13  per  cu.  yd.  for  the  wet 
concrete.  Three  turnings  of  the  stone  with  a  wet  mortar  ef- 
fected a  better  mixture  than  four  turnings  with  a  dry  mortar. 
The  ramming  of  the  wet  concrete  cost  10  cts.  per  cu.  yd., 
whereas  the  ramming  of  the  dry  concrete  cost  75  cts.  per  cu. 
yd.  The  authors  think  this  is  the  highest  cost  on  record  for 
ramming.  It  is  evident,  however,  that  the  men  were  under 
a  poor  foreman,  for  an  output  of  only  15  cu.  yds.  per  day  with 
10  men  is  very  low  for  ordinary  conditions.  Moreover,  the 
expensive  amount  of  ramming  indicates  either  poor  manage- 
ment or  the  most  foolish  inspection  requirements. 

In  conclusion  it  may  b£  noted  that  if  engineers  specify  a 
dry  concrete  and  ''thorough  ramming,"  they  would  do  well 
also  to  specify  what  the  word  "thorough"  is  to  mean,  using 
language  that  can  be  expressed  in  cents  per  cubic  yard.  It  is 
a  common  thing,  for  example,  to  see  a  sewer  trench  specifica- 
tion in  which  one  tamper  is  required  for  each  two  men  shovel- 
ing the  back-fill  into  the  trench ;  and  some  such  specific  re- 
quirement should  be  made  in  a  concrete  specification  if  close 
estimates  from  reliable  contractors  are  desired.  Surely  no 
engineer  will  claim  that  this  is  too  unimportant  a  matter  for 
consideration  when  it  is  known  that  ramming  can  easily  be 
made  to  cost  as  high  as  40  cts.  per  cu.  yd.,  depending  largely 
upon  the  whim  of  the  inspector. 

THE  COST  OF  SUPERINTENDENCE.— This  item  is 
obviously  dependent  upon  the  yardage  of  concrete  handled 
under  one  foreman  and  the  daily  wages  of  the  foreman.  If  a 
foreman  receives  $3  a  day  and  is  bossing  a  job  where  only  12 
cu.  yds.  are  placed  daily,  we  have  a  cost  of  25  cts.  per  cu.  yd. 
for  superintendence.  If  the  same  foreman  is  handling  a  gang 
of  20  men  whose  output  is  50  cu.  yds.,  the  superintendence 
item  is  only  6  cts.  per  cu.  yd.  If  the  same  foreman  is  handling 
a  concrete-mixing  plant  having  a  daily  output  of  150  cu.  yds., 
the  cost  of  superintendence  is  but  2  cts.  per  cu.  yd.  These 
elementary  examples  have  been  given  simply  because  figures 
are  more  impressive  than  generalities,  and  because  it  is  so 
common  a  sight  to  see  money  wasted  by  running  too  small 
a  gang  of  men  under  one  foreman. 

Of  all  classes  of  contract  work,  none  is  more  readily  esti- 
mated day  by  day  than  concrete  work,  not  only  because  it  is 


58  CONCRETE    CONSTRUCTION. 

usually  built  in  regular  shapes  whose  volumes  are  easily  as- 
certained at  the  end  of  each  day,  but  because  a  record  of  the 
bags,  or.  barrels,  or  batches  gives  a  ready  method  of  com- 
puting the  output  of  each  gang.  For  this  reason  small  gangs 
of  concrete  workers  need  no  foreman  at  all,  provided  one  of 
the  workers  is  given  command  and  required  to  keep  tally  of 
the  batches.  If  the  efficiency  of  a  gang  of  6  men  were  to  fall 
off,  say,  15  per  cent.,  by  virtue  of  having  no  regular  non- 
working  foreman  in  charge,  the  loss*  would  be  only  $1.35  a 
clay — a  loss  that  would  be  more  than  counterbalanced  by  the 
saving  of  a  foreman's  wages.  Indeed,  the  efficiency  of  a  gang 
of  6  men  would  have  to  fall  off  25  per  cent.,  or  more,  before 
it  would  pay  to  put  a  foreman  in  charge.  In  many  cases  the 
efficiency  will  not  fall  off  at  all,  provided  the  gang  knows  that 
its  daily  progress  is  being  recorded,  and  that  prompt  discharge 
will  follow  laziness.  Indeed,  one  of  the  authors  has  more  than 
once  had  the  efficiency  increased  by  leaving  a  small  gang  to 
themselves  in  command  of  one  of  the  workers  who  was  re- 
quired to  punch  a  hole  in  a  card  for  every  batch. 

To  reduce  the  cost  of  superintendence  there  is  no  surer 
method  than  to  work  two  gangs  of  18  to  20  men,  side  by  side, 
each  gang  under  a  separate  foreman  who  is  striving  to  make 
a  better  showing  than  his  competitor.  This  is  done  with 
marked  advantage  in  street  paving,  and  could  be  done  else- 
where oftener  than  it  is. 

In  addition  to  the  cost  of  a  foreman  in  direct  charge  of  the 
laborers,  there  is  always  a  percentage  of  the  cost  of  general 
superintendence  and  office  expenses  to  be  added.  In  some 
cases  a  general  superintendent  is  put  in  charge  of  one  or  two 
foremen ;  and,  if  he  is  a  high-salaried  man,  the  cost  of  superin- 
tendence becomes  a  very  appreciable  item. 

SUMMARY  OF  COSTS.— Having  thus  analyzed  the  costs 
of  making  and  placing  concrete,  we  can  understand  why  it  is 
that  printed  records  of  costs  vary  so  greatly.  Moreover,  we 
are  enabled  to  estimate  the  labor  cost  with  far  more  accuracy 
than  we  can  guess  it ;  for  by  studying  the  requirements  of  the 
specifications,  and  the  local  conditions  governing  the  placing 
of  stock  piles,  mixing  boards,  etc.,  we  can  estimate  each  item 
with  considerable  accuracy.  The  purpose,  however,  has  not 
been  solely  to  show  how  to  predict  the  labor  cost,  but  also  to 


HAND   MIXING. 


59 


indicate  to  contractors  and  their  foremen  some  of  the  many 
possibilities  of  reducing  the  cost  of  work  once  the  contract 
has  been  secured.  An  analysis  of  costs,  such  as  above  given, 
is  the  most  effective  way  of  discovering  unnecessary  "leaks,." 
and  of  opening  one's  eyes  to  the  possibilities  of  effecting  econ- 
omies in  any  given  case. 

To  indicate  the  method  of  summarizing  the  costs  of  making 
concrete  by  hand,  let  us  assume  that  the  concrete  is  to  be  put 
into  a  deep  foundation  requiring  wheeling  a  distance  of  30  ft. ; 
that  the  stock  piles  are  on  plank  60  ft.  distant  from  the  mixing 
board ;  that  the  specifications  call  for  6  turns  of  gravel  con- 
crete thoroughly  rammed  in  6-in.  layers;  and  that  a  good 
sized  gang  of,  say,  16  men  (at  $1.50  a  day  each),  is  to  work 
under  a  foreman  receiving  $2.70  a  day.  We  then  have  the 
following  summary  by  applying  the  rules  already  given  : 

Per  cu.  yd. 
concrete. 

Loading  sand,  stone  and  cement ,....$  .17 

Wheeling  60  ft.  in  barrows  (4  +  2  cts.) 06 

Mixing  concrete,  6  turns  at  5  cts 30 

Loading  concrete  into  barrows 12 

Wheeling  30  ft.  (4  +  I  ct.)   05 

Dumping  barrows  (i  man  helping  barrowman) .  .  .      .05 
Spreading  and  heavy  ramming 15 


Total   cost  of   labor $  .90 

Foreman,  at  $2.70  a  day 10 


Grand  total $1.00 

To  estimate  the  daily  output  of  this  gang  of  16  laborers 
proceed  thus:  Divide  the  daily  wages  of  all  the  16  men,  ex- 
pressed in  cents,  by  the  labor  cost  of  the  concrete  in  cents,  the 
quotient  will  be  the  cubic  yards  output  of  the  gang.  Thus, 
2,400-1-90  is  27  cu.  yds.,  in  this  case. 

In  street  paving  work  where  no  man  is  needed  to  help  dump 
the  wheelbarrows,  and  where  it  is  usually  possible  to  shovel 
concrete  direct  from  the  mixing  board  into  place,  and  where 
half  as  much  ramming  as  above  assumed  is  usually  satisfac- 
tory, we  see  that  the  last  four  labor  items  instead  of  amount- 
ing to  12  +  5  +  5  +  15,  or-37  cts.,  amount  only  to  one-half  of 


60  CONCRETE    CONSTRUCTION. 

the  last  item,  one-half  of  15  cts.,  or  jl/2  cts.  This  makes  the 
total  labor  cost  only  60  cts.  instead  of  90  cts.  If  we  divide 
2,400  cts.  (the  total  day's  wages  of  16  men)  by  60  cts.  (the 
labor  cost  per  cu.  yd.),  we  have  40,  which  is  the  cubic  yards 
output  of  the  16  men.  This  greater  output  of  the  16  men  re- 
duces the*  cost  of  superintendence  to  7  cts.  per  cu.  yd. 


CHAPTER  IV. 

METHODS  AND   COST  OF  MAKING  AND   PLACING 
CONCRETE  BY  MACHINE. 

The  making  and  placing  of  concrete  is  virtually  a  manufac- 
turing process.  This  process  as  performed  by  manual  labor 
is  discussed  in  the  preceding  chapter ;  it  will  be  discussed  here 
as  it  is  performed  by  machinery.  The  objects  sought  in  using 
machinery  for  making  and  placing  concrete  are:  (i)  The  se- 
curing of  a  more  perfectly  mixed  and  uniform  concrete,  and 
(2)  the  securing  of  a  cheaper^  cost  of  concrete  in  place.  As  in 
every  other  manufacturing  process  both  objects  cannot  be 
obtained  to  the  highest  degree  without  co-ordinate  and  uni- 
versal efficiency  throughout  in  plant  and  methods.  For  ex- 
ample, the  substitution  of  machine  mixing  for  hand  mixing 
will  not  alone  ensure  cheaper  concrete.  If  all  materials  are 
delivered  to  the  machine  in  wheelbarrows  and  if  the  concrete 
is  conveyed  away  in  wheelbarrows,  the  cost  of  making  con- 
crete even  with  machine  mixers  is  high.  On  the  other  hand, 
where  the  materials  are  fed  from  bins  by  gravity  into  the 
mixer  and  when  the  mixed  concrete  is  hauled  away  in  cars, 
the  cost  of  making  the  concrete  may  be  very  low.  Making 
and  placing-  concrete  by  machinery  involves  not  one  but  sev- 
eral mechanical  operations  working  in  conjunction — in  a  word, 
a  concrete  making  plant  is  required. 

The  mechanical  equipment  of  a  concrete  making  plant  has 
four  duties  to  perform,  (i)  It  has  to  transport  the  raw  mate- 
rials from  the  cars  or  boats  or  pits  and  place  them  in  the  stock 
piles  or  storage  bins ;  (2)  it  has  to  take  the  raw  materials  from 
stock  and  charge  them  to  the  mixer ;  (3)  it  has  to  mix  the  raw 
materials  into  concrete  and  discharge  the  mixture  into  trans- 
portable vehicles;  and  (4)  it  has  to  transport  these  vehicles 
from  the  mixer  to  the  work  and  discharge  them.  As  all  these 
operations  are  interrelated  component  parts  of  one  great 

61 


62  CONCRETE    CONSTRUCTION. 

process,    it   is   plain    why   one   operation    cannot   lag   without 
causing  all  the  other  operations  to  slow  up. 

The  mechanical  devices  which  may  be  used  for  each  of  these 
operations  are  various,  and  they  may  be  combined  in  various 
ways  to  make  the  complete  train  of  machinery  necessary  to 
the  complete  process.  In  this  chapter  we  shall  describe  the 
character  and  qualities  of  each  type  of  devices  separately.  The 
practicable  ways  of  combining  them  to  form  a  complete  con- 
crete making  plant  are  best  illustrated  by  descriptions  and 
records  of  work  of  actual  plants,  and  such  descriptions  and 
records  for  each  class  of  structure  considered  in  this  book  are 
given  in  the  following  chapters  and  may  be  found  by  con- 
sulting the  index.  In  describing  the  various  machines  and 
devices  we  have  made  one  classification  for  those  used  in 
handling  raw  materials  and  mixed  concrete,  for  the  reason 
that  nearly  all  of  them  are  suitable  for  cither  purpose. 

UNLOADING  WITH  GRAB  BUCKETS.— The  orange- 
peel  or  clam-shell  bucket  is  an  excellent  device  for  unloading 
sand  or  stone  from  cars  or  barges.  The  cost  of  unloading,  in- 
cluding cleaning  up  the  portions  not  reached  by  the  bucket, 
is  not  more  than  from  2  to  5  cts.  per  cu.  yd.  A  grab  bucket 
of  either  of  these  types  can  be  applied  to  any  derrick.  In  un- 
loading broken  stone  from  barges  at  Ossining,  N.  Y.,  a  Hay- 
ward  clam-shell  on  a  stiff-leg  derrick  unloaded  TOO  cu.  yds.  of 
broken  stone  per  day  from  barge  into  wagons,  with  one  engine- 
man  and  one  helper.  In  addition  to  the  bucket  work  there  was 
24  hours'  labor  cleaning  on  each  5oo-cu.  yd.  barge  load.  The 
labor  cost  of  unloading  a  5OO-cu.  yd.  barge  was  as  follows : 

Per  Cu.  Yd. 

One  engineman,  at  $2.50 2.5  cts. 

One  helper,  at  $1.50 1.5  cts. 

Labor  cleaning,  at  $1.50 0.7  cts. 


Total  cost  per  cubic  yard ,   4.7  cts. 

INCLINES. — Inclines  to  reach  the  tops  of  mixer  and  stor- 
age bins  and  the  level  of  concrete  work  can  be  operated  on 
about  the  following  grades :  For  teams  hauling  wagons  or 
cars,  2  per  cent,  maximum  grade.  A  single  heavy  team  will 
haul  a  5-cu.  yd.  car,  with  ordinary  bearings,  weighing  2l/2  tons 
empty  and  12  tons  loaded,  with  ease  on  a  ij^  percent,  grade, 


MACHINE  MIXING.  63 

and  with  some  difficulty  on  a  2  per  cent,  grade.  A  locomotive 
will  handle  cars  on  a  grade  of  from  4  to  5  per  cent.  For  team 
haulage  2O-lb.  rails  may  be  used,  and  for  locomotives  3O-lb. 
rails.  Grades  steeper  than  about  5  per  cent,  require  cable 
haulage. 

TRESTLE  AND  CAR  PLANTS.— Trestle  and  car  plants 
for  handling  both  concrete  materials  and  mixed  concrete  have 
a  wide  range  of  application  and  numerous  examples  of  such 
plants  are  described  in  succeeding  chapters,  and  are  noted  in 
the  index  at  the  end  of  the  book.  The  following  estimates  of 
the  cost  of  a  trestle  and  car  plant  are  given  by  Air.  Wm.  G. 
Fargo.  The  work  is  assumed  to  cover  an  area  of  100x200  ft. 
and  to  have  three-fourths  of  its  bulk  below  the  economical 
elevation  of  the  mixer,  which  stands  within  50  ft.  of  the  near 
side  of  the  work.  If  the  work  is  under  3,000  cu.  yds.  in  bulk 
and  there  is  a  reasonable  time  limit  for  completion  one  mixer 
of  200  cu.  yds.  capacity  per  ic-hour  day  is  assumed  to  be  suf- 
ficient. The  items  of  car  plant  cost  will  be  about  as  follows : 

150  ft.  trestle,  at  $1.50 $225 

5  split  switches  with  spring  bridles,  at  $18 90 

2  iron  turntables,  at  $30 60 

3  2/3  cu.  yd.  steel  cars  with  roller  bearing's 190 


Total $565 

The  trestle  assumed  is  double  24-in.  gage  track,  6  ft.  on 
centers  ;  stringers  6X8  ins.  X  22  to  24  ft. ;  ties  2x6  ins.,  2l/2  ft. 
on  centers;  running  boards  2x12  ins.  for  each  track,  and  12-lb. 
rails ;  trestle  legs,  average  length  30  ft.,  of  green  poles  at  5  cts. 
per  foot.  This  outfit  with  repairs  and  renewals  amounting  to 
10  per  cent.,  is  considered  good  for  five  season's  work  and  the 
timber  work  for  several  jobs  if  not  too  far  apart.  The  yearly 
rental  on  the  basis  of  five  seasons'  work  would  be  $124.30,  or 
$i  per  working  day  for  a  season  of  five  months.  Three  cars 
delivering  l/2  cu.  yd.  batches  can  deliver  200  cu.  yds.  of  con- 
crete, an  average  of  100  ft.  from  the  mixer  in  10  hours.  Five 
men,  including  a  man  tending  switches  and  turntable  and  one 
man  to  help  dump,  can  operate  the  plant.  With  wages  at  $1.75 
per  day  the  labor  cost  of  handling  200  cu.  yds.  of  concrete 
would  be  4*4  cts.  per  cu.  yd. 


f)4  COXCIUITE    CONSTRUCTION. 

CABLEWAYS. — Cableways  arranged  to  span  the  work  and 
if  the  area  is  wide  to  travel  across  the  work  at  right  angles  to 
the  span  will  handle  concrete,  concrete  materials,  forms,  steel 
and  supplies  with  great  economy.  They  are  particularly  suit- 
able for  bridge  and  dam  work,  filter  and  reservoir  work,  build- 
ing foundations  and  low  buildings.  The  arrangement  of  a 
cableway  plant  for  bridge  work  is  described  in  Chapter  XVII. 
A  cableway  of  800  ft.  clear  span  on  fixed  towers  45  ft.  high  will 
cost  complete  from  $4,500  to  $5,000,  and  will  handle  200  cu. 
yds.  of  concrete  per  lo-hour  day.  To  put  the  cableway  on 
traveling  towers  will  cost  about  $1,000  more.  In  constructing 
the  Pittsburg  filtration  work  four  traveling  cableways  from 
250  to  600  ft.  span  were  used.  The  towers  were  from  50  to 
60  ft.  in  height  and  each  traveled  on  a  5-rail  track.  The  cable- 
ways  were  self-propelling.  With  conditions  favorable  each 
cableway  delivered  300  cu.  yds.  of  concrete  per  day.  A  cable- 
way  plant  for  heavy  fortification  work  is  described  in  Chap- 
ter XL 

BELT  CONVEYORS.— Belt  conveyors  may  be  used  suc- 
cessfully for  handling  both  concrete  materials  and  mixed  con- 
crete. For  handling  wet  concrete  the  slope  must  be  quite  flat, 
and  the  belt  must  be  provided  with  some  means  of  cleaning 
off  the  sticky  mortar  paste.  In  several  cases  rotating  brushes 
stationed  at  the  end  of  the  belt,  where  it  turns  over  the  tail 
pulley,  have  worked  successfully;  these  brushes  sweep  the  belt 
clean.  Except  for  the  cleaning  device  the  ordinary  arrange- 
ment of  belt  conveyor  for  dry  materials  serves  for  concrete. 

In  constructing  a  large  gas  works  at  Astoria,  Long  Island, 
near  New  York  city,  belt  conveyors  were  used  to  handle  both 
the  sand,  gravel  and  cement  bags  and  the  mixed  concrete. 
The  belt  for  handling  sand  and  gravel  is  shown  by  Fig,  13.  A 
derrick  operating  a  clam-shell  unloaded  the  sand  and  gravel 
into  a  small  hopper,  discharging  into  dump  cars  operated,  by 
a  "dinky"  up  an  incline,  passing  over  sand  and  gravel  storage 
bins.  A  2O-in.  belt  conveyor  ran  horizontally  105  ft.  under  the 
bins,  then  up  an  incline  of  3.4  ft.  in  125  ft.  to  feeding  hoppers 
over  the  mixers.  This  conveyor  received  alternately  sand  and 
gravel  by  chute  from  the  storage  bins  and  bags  of  cement 
loaded  by  hand,  and  carried  them  to  the  feeding  bins  and 
mixer  platform.  The  speed  of  the  belt  was  350  ft.  per  minute, 


MACHINE  MIXING. 


and  it  required  6  h.p.  to  operate  it  when  carrying  100  tons  per 
hour.  The  mixing  was  done  in  two  Smith  mixers,  which 
turned  out  70  cu.  yds.  or  35  cu.  yds.  each  per  hour.  The 
mixed  concrete  was  delivered  onto  a  5O-ft.  24-in.  belt  con- 
veyor traveling  at  a  speed  of  400  ft.  per  minute  and  dumping 
through  a  chute  into  cars.  Only  i  h.p.  was  required  to  run 
the  concrete  conveyor.  A  rotating  brush  was  used  to  keep 
the  belt  clean  at  the  dumping  end.  It  will  be  noted  that  only 
a  small  amount  of  power  is  required  for  operation. 


•BeH- 


TracJf 


,-Belt 


Fig.   13. — Belt  Conveyor  Transporting  Sand  and  Gravel. 

CHUTES. — Chutes  of  wood  or  iron  are  among  the  simplest 
and  most  efficient  means  of  moving  the  cement,  sand  and 
stone  and  the  mixed  concrete  when  the  ground  levels  permit 
such  devices. 

Bags  of  cement  if  given  a  start  in  casting  will  slide  down 
a  steel  or  very  smooth  wooden  chute  with  a  slope  of  i  ft.  in  5 
or  6  ft.  A  wooden  trough  12  ins.  deep  and  24  ins.  wide  with 
boards  dressed  on  the  inside  may  be  used.  When  the  inclina- 
tion is  steep  and  the  fall  is  great,  some  device  is  necessary  to 
diminish  the  velocity  of  descent ;  the  following  is  an  example 
of  such  a  device  which  was  successfully  employed  in  a  chute 
of  the  above  dimensions,  400  ft.  long  and  having  a  drop  of 
110  ft.  This  chute  had  a  maximum  inclination  of  45°  and  its 
lower  end  curved  to  a  horizontal  tangent,  running  into  the 
storehouse.  Near  the  bottom  of  the  chute  a  horizontal  strip 
was  nailed  across  the  upper  edges  and  to  it  was  nailed  the 
upper  end  of  a  20  ft.,  ixi2-in.  board,  the  lower  end  of  which 
rested  on  the  bottom  of  the  chute.  Several  pieces  of  timber 
spiked  to  the  upper  side  loaded  the  lower  end  of  this  board. 


66  CONCRETE    CONSTRUCTION. 

The  cement  bag  in  descending  wedged  itself  into  the  angle  be- 
tween the  chute  and  the  board  and  lifted  the  latter,  the  spring 
of  the  board  and  the  weight  at  the  lower  end  offering  enough 
resistance  to  cut  down  the  velocity.  After  the  chute  had  been 
in  use  for  some  time  and  had  worn  smooth  it  was  found  neces- 
sary to  add  two  more  brakes  to  check  the  bags. 

Broken  stone  will  slide  down  a  steel  or  steel  lined  chute 
with  a  slope  of  I  in  3  or  4  ft.  if  given  a  start  in  casting.  Damp 
sand  will  not  slide  down  a  chute  with  a  slope  of  il/2  in  i. 

A  wet  cement  grout  will  flow  down  a  smooth  plank  chute, 
with  a  slope  of  I  in  4  ft.,  and  wet  concrete  will  move  on  the 
same  slope;  comparatively  dry  concrete  requires  a  slope  of 
nearly  i  in  i,  or  45°,  to  secure  free  movement.  Mr.  W.  J. 
-Douglas  gives  the  following  examples  of  conveying  concrete 
by  chute,  prefaced  by  the  statement  that  his  experience  indi- 
cates that  concrete  can  thus  be  conveyed  considerable  dis- 
tances without  material  injury  if  proper  precautions  are  taken. 

In,  the  first  case  a  semi-circular  steel  trough  about  2  ft.  wide 
and  i  ft.  deep  and  15  ft.  long  set  on  a  slope  of  45°  w'as  used. 
A  lift  gate  ol  sheet  steel  was  set  in  the  chute  about  2  ft.  from 
the  upper  end.  The  concrete  was  allowed  to  accumulate  be- 
hind this  gate  until  a  wheelbarrow  load  was  had,  when  the 
batch  was  let  loose  by  lifting  the  gate  and  was  discharged 
into  barrows  at  the  bottom.  In  another  case  a  vertical  chute 
15  ft.  long,  consisting  of  a  I5~in.  square  box  with  a  canvas 
end,  was  used.  The  concrete  was  dumped  into  the  chute  in 
batches  of  about  8  cu.  ft. ;  t\vo  men  at  the  bottom  "cut  down" 
the  pile  with  hoes  to  keep  it  from  coning  and  causing  separa- 
tion of  the  stone.  In  a  third  case  a  continuous  mixer  fed  into 
a  sheet  iron  lined  rectangular  chute  about  2l/2  ft.  wide  and  i 
ft.  deep,  with  a  vertical  drop  of  60  ft.  on  a  slope  of  i  in  i,  or 
45°.  A  gate  was  fixed  in  the  chute  2  ft.  from  the  top  and  at 
the  bottom  the  chute  fed  into  a  pyramidal  hopper  3  ft.  square 
at  the  top,  i  ft.  square  at  the  bottom  and  4l/2  ft.  deep.  This 
hopper  was  provided  with  a  bottom  gate  and  was  set  on  legs 
so  that  its  top  was  about  10  ft.  above  ground.  As  the  con- 
crete filled  in  the  hopper  was  raised  and  the  chute  cut  off.  The 
hopper  was  kept  full  all  the  time  and  was  discharged  by  bot- 
tom gate  and  spout  into  wheelbarrows.  In  a  fourth  case  the 
apparatus  shown  by  the  sketch,  Fig.  14,  was  used.  The  con- 


MACHINE   MIXING. 


67 


tinuous  mixer  discharged  onto  an  i8-in.  rubber  conveyor  belt 
on  conical  rollers  and  18  ft.  long.  The  inner  end  of  the  con- 
veyor frame  was  carried  on  the  ground  at  the  edge  of  the  pit 
and  the  outer  end  was  supported  by  ropes  from  the  top  of  a 
gallows  frame  standing  on  the  pit  bottom.  The  belt  dis- 
charged over  end  into  a  vertical  steel  chute  12  ins.  in  diam- 
eter and  8  ft.  long;  this  chute  was  fastened  to  the  conveyor 
frame.  Encircling  and  overlapping  the  12-in.  chute  was  a 
second  slightly  larger  chute  suspended  by  means  of  two  ropes 
from  the  gallows  frame.  The  bottom  of  this  second  chute 
was  kept  about  6  ins.  below  the  top  edges  of  a  pyramidal  hop- 
per like  the  one  described  above.  In  operation  the  chutes 
and  the  hopper  were  kept  rilled  with  concrete  so  that  the  only 
drop  of  the  concrete  was  3  ft.  from  the  conveyor  belt  into  the 
topmost  chute. 


Fig.  14.— Belt  Conveyor  and  Chute  for  Handling  Concrete. 

Concrete  may  be  handled  in  long  flat  chutes  by  stationing 
men  along  the  chute  with  shovels  which  they  work  like  pad- 
dles to  keep  the  mixture  moving.  In  one  case  concrete  was  so 
handled  in  a  chute  200  ft.  long  having  a  slope  of  I  in  10  ft. 
The  chute  was  a  V-shaped  trough  made  of  i  x  12-in.  boards 
in  sections  16  ft.  long.  The  men  paddling  were  stationed  10  ft. 
apart,  sc  that  with  wages  at  $1.50  per  day  the  cost  would 
be  il/2  cts.  per  cu.  yd.  for  every  10  ft.  the  concrete  was  con- 
veyed. In  connectiton  with  this  particular  work  we  are  in- 
formed that  a  Eureka  continuous  mixer  was  used.  The  gravel 
was  dumped  near  the  mixer  and  a  team  hitched  to  a  drag 
scraper  delivered  the  gravel  alongside  the  mixer.  Four  men 
shoveled  the  gravel  into  the  measuring  hopper,  but  only  two 
men  worked  at  a  time,  shoveling  for  a  period  of  15  minutes 


68  CONCRETE    CONSTRUCTION. 

and  then  resting  for  a  corresponding  period  while  the  other 
two  men  worked.  In  this  manner  the  four  men  shoveled 
enough  gravel  to  make  100  cu.  yds.  of  concrete  per  day.  A 
fifth  man  opened  the  cement  bags  and  kept  the  cement  hopper 
filled. 

METHODS  OF  CHARGING  MIXERS.— By  charging  is 
meant  the  process  of  delivering  raw  materials  from  stock 
into  the  mixer.  Several  methods  are  practiced  and  will  be 
considered  in  the  following  order:  (i)  By  gravity  from  over- 
head bins ;  (2)  by  wheelbarrow  or  hand  cart  (a)  to  charging 
chute  and  (b)  to  elevating  charging  hoppers ;  (3)  by  charging 
cars  operated  by  cable  or  other  means ;  (4)  by  shoveling 
directly  into  mixer;  (5)  by  derricks  or  other  hoists. 

Charging  by  Gravity  from  Overhead  Bins. — Chitting  the 
sand  and  stone  from  overhead  bins  to  the  charging  hopper 
is  a  simple,  rapid  and  economical  method  of  charging  mixers. 
The  bottoms  of  the  bins  should  always  be  high  enough  above 
the  charging  floor  to  give  ample  head  room  for  men  to  move 
about  erect,  and  the  length  of  chute  may  be  anything  reason- 
able more  than  this  that  conditions  such  as  the  side  hill 
delivery  of  material  may  necessitate.  When  the  mixer  is 
located  to  one  side  of  the  bins  the  slope  of  the  chute  will 
have  to  be  watched.  Broken  stone  or  pebbles  will  move  on 
a  comparatively  flat  slope  but  sand,  particularly  if  damp,  re- 
quires a  steep  chute.  The  measuring  hopper  is  best  kept  en- 
tirely independent  of  the  mixer  so  that  it  can  be  filled  with  a 
new  charge  while  the  mixer  is  turning  and  discharging  the 
preceding  batch.  One  man  can  attend  the  sand  and  cement 
chutes  if  they  be  conveniently  arranged,  and  one  man  can 
open  and  empty  the  cement  bags  if  they  be  stacked  close  at 
hand.  A  third  man  will  level  off  the  sand  and  stone  in  the 
measuring  hopper  and  help  in  the  chuting.  A  gang  of  this 
size  will  easily  measure  up  a  charge  every  2  minutes  when 
no  delays  occur. 

A  number  of  plants  charging  by  gravity  from  overhead  bins 
are  described  in  succeeding  chapters  and  are  referenced  in  the 
index.  As  a  general  example  a  side  hill  plant  of  conventional 
construction  is  shown  by  Fig.  15.  The  trestle  work  was  made 
of  12  x  12-in.  timbers  and  was  approximately  40  ft.  in  height. 
Three  tracks  occupy  the  top  platform.  Under  each  track  was 


MACHINE    MIXING.  69 

a  material  bin ;  one  on  each  side  for  gravel  and  a  middle  bin 
for  sand.  The  sand  bin  was  divided  by  a  partition  into  two 
compartments.  These  bins  discharged  into  two  measuring 
hoppers  one  gravel  bin  and  one  compartment  of  the  sand 
bin  into  each  hopper.  Two  cement  chutes  from  the  top  plat- 
form provided  for  the  delivery  of  the  cement  to  the  mixers, 
either  directly  from  cars  or  from  the  cement  storage  house. 
The  mixing  was  done  in  two  Smith  No.  5  mixers,  one  under 
each  measuring  hopper,  and  these  mixers  discharged  by 
chutes  into  buckets  on  flat  cars.  Thus  the  concrete  materials 
brought  directly  from  a  siding  in  car  load  lots  to  the  top  of 
the  platform  were  handled  entirely  by  gravity  to  the  cars  de- 
livering the  mixed  concrete  to  the  work.  The  <^ang  operating 
the  mixing  plant,  with  the  wages  paid,  was  composed  as 


3  JracHs  From 
Stiinq 


Fig.    15. _ Side    Hill    Mixing    Plant. 

follows :  i  foreman  and  engineer  at  $3  per  day,  i  fireman  at 
$2  per  day  and  15  laborers  at  $1.50  per  day.  With  this  gang 
the  two  mixers  turned  out  400  cu.  yds.  of  concrete  per  day 
and,  frequently,  800  cu.  yds.  in  24  hours.  Taking  these  figures 
the  labor  cost  from  raw  materials  in  cars  on  the  platform 
to  mixed  concrete  in  cars  on  the  delivery  track  was  as 
follows : 

i   foreman  and  engineer  at  $3   .  .  . - $  3-°° 

i   fireman   at  $2    '  *-°° 

15  laborers  at  $1.50    •   22-5° 

Total  labor  ..$27.50 

Assuming  400  cu.  yds.  output,  this  gives  a  cost  of  $27.50 -f- 

400  =  6.875 cts-  Per  cu-  y^ 


70  CONCRETE    CONSTRUCTION. 

Charging  with  Wheelbarrows. — The  economics  of  wheel- 
barrow haulage  are  discussed  in  some  detail  in  Chapter  III. 
For  machine  mixer  work  the  problem  of  loading-,  transport- 
ing and  dumping  is  complicated  by  the  greater  rapidity  with 
which  the  mixing  is  done  and  by  the  necessity,  usually,  of 
using  inclines  to  reach  the  charging  hopper  level.  The  in- 
cline cuts  down  the  output  of  the  wheelers  or  in  other  words 
makes  necessary  a  larger  gang  to  handle  the  same  amount  of 
material.  Conditions  being  the  same,  the  height  of  the  charg- 
ing chute  of  the  mixer  determines  the  height  of  incline  and 
the  size  of  the  charging  gang,  so  that  a  mixer  with  a  high 
charging  level  costs  more  to  charge  with  wheelbarrows  than 
does  one  with  a  low  charging  level.  Exact  figures  of  the  in- 
creased cost  of  a  few  feet  extra  elevation  of  the  wheelbarrow 
incline  are  not  available,  but  some  idea  may  be  had  from  a 
brief  calculation.  The  materials  for  a  cubic  yard  of  concrete 
will  weigh  about  3,700  Ibs.,  so  that  to  raise  the  materials  for 
100  cu.  yds.  of  concrete,  including  weight  of  barrows,  I  ft. 
calls  for  about  400,000  ft.  Ibs.  of  work.  A  man  will  do  about 
800,000  ft.  Ibs.  of  useful  work  in  a  day,  so  that  each  foot  of 
additional  height  of  incline  means  an  additional  half-day's 
work  for  one  man. 

Wheeling  to  elevating  charging  hoppers  obviates  the  use 
of  inclines.  Figure  19  shows  a  mixer  equipped  with  such 
a  hopper,  and  the  arrangement  provided  for  other  makes  of 
mixer  is  much  similar.  When  the  hopper  is  lowered  ready  to 
receive  its  load  its  top  edge  over  which,  the  wheelbarrows  are 
dumped  is  from  12  to  14  ins.  above  ground  level.  The  wheel- 
ing is  all  done  on  the  level.  The  elevating  bucket  is  operated 
by  the  mixer  engine  and  is  usually  detachable.  Where  mixers 
have  to  be  moved  frequently,  requiring  the  erection  and  mov- 
ing of  the  incline  each  time,  an  elevating  charging  hopper  is 
particularly  useful;  it  can  be  hoisted  clear  of  the  ground 
and  moved  with  the  mixer,  so  that  it  is  ready  to  use  the 
moment  that  the  mixer  is  set  at  its  new  station. 

While  the  ordinary  wheelbarrow  is  generally  used  for 
charging,  better  work  can  be  done  under  some  conditions  by 
using  special  charging  barrows  of  larger  capacity  and  dump- 
ing from  the  end  and  ahead  of  the  wheel.  Two  forms  of 
charging  barrow  are  shown  by  Figs.  16  and  17.  The  Acme 


MACHINE   MIXING.  7! 

barrow  will  hold  4  cu.  ft.  and  the  Ransome  barrow  is  made  in 
3  to  6  cu.  ft.  capacities.  Where  inclines  are  necessary  these 
barrows  can  often  be  hauled  up  the  incline  by  power.  A 
sprocket  chain  in  the  plane  of  the  incline  and  operated  by  the 


is. — Forward   Dump   Charging  Barrow,   Sterling  Wheelbarrow  Co. 


Fig.  17.— Forward  Dump  Charging  Barrow,  Ransome  Concrete  Machinery  Co. 

mixer  engine  is  an  excellent  arrangement.  A  prOng  riveted  to 
the  rear  face  of  the  barrow  and  projecting  downward  is 
"caught  into"  the  chain,  which  pulls  the  barrow  to  the  top, 
the  man  following  to  dump  and  return  for  another  load. 


72  CONCRETE    CONSTRUCTION. 

4» 

Charging  with  Cars. — Cars  moved  by  cable,  team  or  hand 
are  a  particularly  economic  charging  device  when  the  mixer 
is  located  a  little  distance  from  the  stock  piles  or  bins.  Either 
separate  cars  for  cement,  sand  and  stone,  each  .holding  the 
proper  amount  of  its  material  for  a  batch,  can  be  used,  or  a 
single  car  containing  enough  of  all  three  materials  for  a  batch. 
The  last  arrangement  is  ordinarily  more  economical  in  time 
and  labor,  and  in  plant  required.  In  either  case  the  oar  serves 
as  the  measuring  hopper,  there  being  no  further  proportioning 
of  the  materials  after  they  have  been  loaded  into  the  car,  and 
it  must  be  arranged  for  measuring.  Usually  all  that  is  neces- 
sary, where  one  car  is  used,  is  to  mark  the  levels  on  the  sides 
to  which  it  is  to  be  filled  with  sand  and  then  stone ;  the  car  is 
run  to  the  sand  stock  and  filled  to  the  level  marked  for  sand 
and  then  to  the  stone  stock  and  filled  to  the  level  marked  foi 
stone.  The  cement  may  be  added  to  the  charge  either  before 
or  after  it  is  run  to  the  mixer  as  convenience  in  storing  the 
cement  stock  dictates.  Instead  of  having  marks  to  show  the 
proper  proportions  of  sand  and  stone,  the  car  is  sometimes 
divided  into  two  compartments,  one  for  each  material  and 
each  holding  the  proper  proportion  of  its  material  when  level 
full.  This  arrangement  makes  proper  proportioning  some- 
what more  certain,  since  the  men  charging  the  car  cannot 
over-run  the  marks.  In  case  separate  cars  are  used  for  each 
material,  they  are  simply  filled  level  full  or  to  mark,  and 
dumped  in  succession  into  the  feeding  hopper.  Trestle  and 
car  plant  construction  and  costs  are  given  in  a  preceding 
section. 

Charging  by  Shoveling. — Charging  by  shoveling  directly 
into  the  mixer  is  seldom  practiced  except  in  street  work  with 
continuous  mixers  or  in  charging  gravity  mixers  of  the  trough 
type.  Shoveling  is  not  an  economic  method  of  handling  ma- 
terials where  the  work  involves  carrying  in  shovels,  and  it  is 
only  in  a  few  classes  of  concrete  work  or  in  isolated,  excep- 
tional cases  that  charging  with  shovels  does  not  involve 
carrying.  The  amount  of  material  that  men  will  load  with 
shovels  is  given  in  Chapter  III,  and  the  reader  who  wishes 
a  full  discussion  of  the  subject  is  referred  to  Gillette  and 
Hauer,  "Earth  Excavation  and  Embankments;  Methods  and 
Cost." 


MACHINE   MIXING.  73 

In  charging  continuous  mixers  with  shovels  the  usual  prac- 
tice for  mixers  without  automatic  feed  devices  is  to  work 
from  a  continuous  stock  pile  of  sand,  stone  and  cement  spread 
in  layers  in  the  proper  proportions.  The  shoveling  is  done  in 
such  a  manner  that  each  shovelful  contains  a  mixture  of  ce- 
ment, sand  and  stone,  and  so  that  the  rate  of  delivery  to  the 
mixer  is  as  uniform  as  possible.  In  charging  mixers  having 
automatic  feed  devices  the  sand  and  stone  are  simply  shoveled 
into  the  sand  and  stone  hoppers,  whence  they  are  fed  auto- 
matically to  the  mixer.  In  charging  gravity  mixers  by  shovel- 
ing the  method  is  essentially  the  same ;  the  cement,  sand  and 
stone  properly  proportioned  are  spread  in  layers  on  "the  shov- 
eling board  at  the  head  of  the  mixer  and  the  mixture  then 
shoveled  into  the  mixer.  In  both  of  these  cases  mixing  is 
performed  to  a  certain  extent  by  the  shoveling,  and  in  both 
the  provision  of  the  combination  stock  pile  from  which  the 
men  work  involves  labor  which  comes  within  the  meaning  of 
the  term  charging  as  we  have  used  it  here.  Examples  of  street 
work  in  which  the  mixers  were  charged  by  shoveling  are 
given  in  Chapter  XIV. 

Charging  with  Derricks. — When  the  stock  piles  are  located 
close  to  the  mixer  and  the  plant  is  fixed  or  is  not  frequently 
moved  derricks  can  be  used  economically  for  charging,  par- 
ticularly if  the  mixer  be  elevated  so  that  inclines  become  ex- 
pensive. The  following  mode  of  operation  will  be  found  to 
work  well :  Set  the  derrick  so  that  its  boom  "covers"  the 
sand  and  stone  piles  and  the  mixer,  and  provide  it  with 
three  buckets  so  that  there  will  always  be  one  bucket  at  the 
stone  pile  and  another  at  the  sand  pile  while  the  third  is  being 
handled.  The  derrick  swinging  from  the  mixer,  where  it  has 
discharged  a  bucket,  drops  the  empty  bucket  at  the  stone  pile 
and  picks  up  the  bucket  standing  there,  which  has  received 
its  proper  charge  of  stone,  and  swings  it  to  the  sand  pile  and 
drops  it  to  get  its  charge  of  sand.  Here  it  picks  up  the  bucket 
standing  at  the  sand  pile  and  which  has  its  charges  of  both 
stone  and  sand,  and  swings  it  to  the  mixer.  By  this  arrange- 
ment the  work  of  the  derrick  and  of  the  men  filling  the 
buckets  is  practically  continuous.  The  buckets  can  be  pro- 
vided with  marks  on  the  inside  to  show  the  proper  points 
to  which  to  fill  the  stone  and  the  sand  or  a  partition  may  be 


74 


CONCRETE    CONSTRUCTION. 


riveted  in  making  a  compartment  for  sand  and  another  for 
stone.  A  special  charging  bucket  that  is  arranged  with  a 
wheel  and  detachable  handles  which  permit  it  to  be  handled 
like  a  wheelbarrow  is  shown  by  Fig.  18.  This  bucket  can  be 
used  to  advantage  where  the  stock  piles  are  too  far  from  the 
mixer  for  the  derrick  to  reach  both,  the  bucket  being  loaded 
and  wheeled  to  within  reach  of  the  derrick. 


Fig.  18.— Charging  Bucket  With  Wheel  and  Detachable  Handle. 

TYPES  OF  MIXERS.— There  are  two  types  of  concrete 
mixing  machines  or  concrete  mixers  as  they  are  more  com- 
monly called:  (i)  Batch  mixers  and  (2)  continuous  mixers. 
In  mixers  of  the  first  type  a  charge  of  cement,  sand,  aggre- 
gate and  water  is  put  into  the  machine  which  mixes  and  dis- 
charges the  batch  before  taking  in  another  charge;  charging, 
mixing  and  discharging  is  done  in  batches.  In  continuous 
mixers  the  cement  sand,  stone  and  water  are  charged  into  the 
machine  in  a  continuous  stream  and  the  mixed  concrete  is  dis- 
charged in  another  continuous  stream.  While  all  concrete 
mixers  are  either  batch  or  continuous  mixers  it  is  common 
practice  because  of  their  distinctive  character  to  separate  grav- 
ity mixers,  whether  batch  or  continuous,  into  a  third  type. 
In  gravity  mixers  the  concrete  materials  are  made  to  mingle 
by  falling  through  specially  constructed  troughs,  or  tubes,  or 
hoppers.  We  shall  describe  mixers  in  this  chapter  as  (i) 
batch  mixers,  (2)  continuous  mixers,  and  (3)  gravity  mixers. 
No  attempt  will  be  made,  however,  to  describe  all  or  even  all 
the  leading  mixers  of  each  type;  a  representative  mixer  or 


MACHINE   MIXING. 


75 


two  of  each  type  will  be  described,  enough  to  give  an  indica- 
tion of  the  range  of  practice,  and  the  reader  referred  to  manu- 
facturers' literature  for  further  information. 

Batch  Mixers. — Batch  mixers  are  made  in  two  principal 
forms  which  may  be  designated  as  titling  and  non-tilting 
mixers.  In  the  first  form  the  mixer  drum  is  tilted  as  one 
would  tilt  a  bucket  of  water  to  discharge  the  batch.  In  non- 
tilting  mixers  the  mixer  drum  remains  in  one  position,  the 
batch  being  discharged  by  special  mechanism  which  dips  it 
out  a  portion  at  a  time.  In  both  forms  the  charge  is  put  into 
the  mixer  as  a  unit  and  kept  confined  as  a  unit  during  the 
time  of  mixing,  which  may  be  any  period  wished  by  the 
operator. 


Fig.    19.— Chicago    Improved   Cube   Concrete   Mixer  with   Elevating   Charging 

Hopper. 

Chicago  Improved  Cube  Tilting  Mixer.— Figure  19  shows 
the  improved  cube  mixer  made  by  the  Municipal  Engineering 
&  Contracting  Co.,  Chicago,  111.  The  drum  consists  of  a 
cubical  box  with  rounded  corners  and  edges.  This  box  has 
hollow  gudgeons  at  two  diagonally  opposite  corners  and 
these  gudgeons  are  open  as  shown  to  provide  for  charging 


76 


CONCRETE    CONSTRUCTION. 


and  discharging.  The  box  is  rotated  by  gears  mesh- 
ing with  a  circumferential,  rack  midway  between  gudgeons 
and  another  set  of  gears  operate  to  tilt  the  mixer.  The 
inside  of  the  box  is  smooth,  there  being  no  deflectors,  as  its 
shape  is  such  as  to  fold  the  batch  repeatedly  and  thus  accom- 
plish the  mixing. 

Ransome  Non-Tilting  Mixer. — Figure  20  shows  a  repre- 
sentative non-tilting  mixer  made  by  the  Ransome  Concrete 
Machinery  Co.,  Dunellen,  N.  J.  It  consists  of  a  cylindrical 


Fig.    20. — Ransome   Concrete   Mixer. 

drum  riding  on  rollers  and  rotated  by  a  train  of  gears  meshing 
with  circumferential  racks  on  the  drum.  The  drum  has  a  cir- 
cular opening  at  each  end;  a  charging  chute  enters  one  open- 
ing and  a  tilting  discharge  chute  may  be  thrown  into  or  out 
of  the  opposite  opening.  The  cylindrical  shell  of  the  drum  is 
provided  inside  with  steel  plate  deflectors,  which  plow 
through  and  pick  up  and  drop  the  concrete  mixture  as  the 
drum  revolves.  The  shape  and  arrangement  of  the  deflectors 
are  such  that  the  batch  is  shifted  back  and  forth  axially  across 


MACHINE   MIXING.  77 

the  mixer.  To  discharge  the  batch  the  discharge  chute  is 
tilted  so  that  its  end  projects  into  the  mixer,  in  which  position 
the  material  picked  up  by  the  deflectors  drops  back  onto  the 
chute  and  runs  out.  The  discharge  chute  being  independent 
of  the  mixing  drum  it  can  be  thrown  into  and  out  of  discharge 
position  at  will  without  stopping  the  rotation  of  the  drum,  and 
so  can  discharge  any  part  or  all  of  the  batch  at  once.  The 
top  edge  of  the  charging  chute  ranges  from  30^  to  38  ins.  in 
height  above  the  top  of  the  frame,  varying  with  the  size  of 
the  mixer. 


Fig.   21. — Smith   Concrete  Mixer. 

Smith  Tilting  Miver. — Figure  21  shows  a  tilting  mixer, 
known  as  the  Smith  mixer,  made  by  the  Contractors'  Supply 
&  Equipment  Co.,  Chicago,  111.  The  drum  consists  of  two 
truncated  cones  with  their  large  ends  fastened  together  and 
their  small  ends  open  for  receiving  the  charge  and  discharge 
of  the  batch.  The  drum  is  operated  by  a  train  of  gears  mesh- 
ing into  a  rack  at  mid-length  where  the  cones  join.  In  addi- 
tion there  is  another  set  of  gears  which  tilt  the  drum  to  make 
the  concrete  flow  out  of  the  discharge  end.  The  inside  of  the 
drum  is  provided  with  steel  plate  deflectors,  which  plow 
through  and  pick  and  drop  the  concrete  mixture  shifting  it 
back  and  forth  axially  in  the  process. 


^8  CONCRETE    CONSTRUCTION. 

Continuous  Mixers. — Continuous  mixers  are  those  in  which 
the  cement,  sand  and  stone  are  fed  to  the  charging  hopper  in  a 
continuous  stream  and  the  mixed  concrete  is  discharged  in 
another  continuous  stream.  They  are  built  in  two  principal 
forms.  In  one  form  the  cement,  sand  and  stone  properly 
proportioned  are  shoveled  directly  into  the  mixing  drum.  In 
the  other  form  these  materials  are  dumped  into  separate 
charging  hoppers  and  are  automatically  fed  into  the  mixing 
drum  in  any  relative  proportions  desired.  One  form  of  con- 
tinuous mixer  with  automatic  feed  is  described  in  the  succeed- 
ing paragraph  and  another  form  is  described  in  Chapter  XIV. 


Fig.  22. — Eureka  Automatic   Feed  Continuous  Mixer. 

The  continuous  mixer  without  automatic  feed  consists  simply 
of  a  trough  with  a  rotating  paddle  shaft  and  its  driving 
mechanism.  The  charging,  the  mixing  and  the  discharging 
are  done  in  what  is  virtually  a  succession  of  very  small 
batches. 

Eureka  Automatic  Feed  MLvcr. — Figure  22  shows  the  con- 
struction of  the  continuous  mixer  built  by  the  Eureka  Machine 
Co.,  Lansing,  Mich.  The  cement  bin  and  feeder  is  the  small 
one  in  the  foreground.  There  is  a  pocketed  cylinder  revolving 
between  concave  plates,  opening  into  the  hopper  above,  from 
which  the  pockets  in  the  feeder  are  filled,  and  discharging 


MACHINE   MIXING.  79 

directly  into  the  mixing  trough  below.  Back  of  this  is  shown 
the  feeder  for  sand  or  gravel  up  to  2-in.  screen  size.  This  is  a 
pocketed  cylinder  similar  to  that  used  in  the  cement  feeder, 
except  that  it  is  larger,  and  instead  of  being  provided  on  the 
discharge  side  with  a  concave  plate,  is  surmounted  by  a  roller, 
held  by  springs.  This  serves  to  cut  off  the  excessive  flow  of 
material,  but  provides  sufficient  flexibility  to  allow  the  rough 
coarse  material  to  be  fed  through  the  machine  without  its 
catching.  The  feeder  for  crushed  stone  is  a  similar  construc- 
tion on  larger  lines,  to  handle  material  up  to  3-in.  size.  These 
several  feeders  can  be  set  to  give  any  desired  mixture.  On 
any  material  fit  to  be  used  in  concrete,  they  will  measure  with 
an  error  of  less  than  5  per  cent.,  an  agitator  being  provided 
in  the  sand  bin  to  prevent  damp  sand  from  bridging  over  the 
feeder,  and  preventing  its  action.  The  mixer  consists  of  a 
trough,  with  a  square  shaft,  on  which  are  mounted  37  mixing 
paddles,  which  are  slipped  on  in  rotation,  so  as  to  form  prac- 
tically a  continuous  conveyor,  but  as  each  paddle  is  distinct, 
and  is  shaped  like  the  mold  board  of  a  plow,  the  material,  as  it 
passes  from  one  to  the  next,  is  turned  over  and  stirred.  Water 
is  sprayed  into  the  mass  at  the  center  of  the  trough.  The 
result  is  a  dry  mix,  followed  by  a  wet  mix.  The  mixing  trough 
is  made  of  heavy  gage  steel,  well  reinforced,  and  practically 
indestructible.  To  take  care  of  the  discharge  of  material  while 
changing  wheelbarrows,  a  hood  is  provided  on  the  discharge 
end  of  the  machine,  which  can  be  lowered,  and  will  hold  about 
a  wheelbarrow  load. 

Gravity  Mixers. — Gravity  mixers  are  constructed  in  two 
general  forms.  The  first  form  is  a  trough  whose 'bottom  or 
sides  or  both  are  provide^  with  pegs,  deflectors  or  other  de- 
vices for  giving  the  material  a  zig-zag  motion  as  it  flow* 
down  the  trough.  The  second  form  consists  of  a  series  of 
hoppers  set  one  above  the  other  so  that  the  batch  is  spilled 
from  one  into  the  next  and  is  thus  mixed. 

The  chief  advantage  claimed  for  gravity  mixers  is  that  no 
power  is  required  to  operate  them.  This  is  obviously  so  only 
in  the  sense  that  gravity  mixers  have  no  power-operated 
moving  mechanism,  and  the  fact  should  not  be  overestimated. 
The  cost  of  powrer  used  in  the  actual  performance  of  mixing  is 
a  very  small  item.  The  distance  between  feed  and  discharge 


8o 


CONCRETE    CONSTRUCTION. 


levels  is  always  greater  for  gravity  mixers  than  for  machine 
mixers,  and  the  power  required  to  raise  the  concrete  materials 
the  excess  height  may  easily  be  greater  than  the  power  re- 
quired to  operate  a  machine  mixer.  On  the  other  hand  the 

simplicity  of  the  gravity  mixer 
insures  low  maintenance  costs. 
GUbreth  Trough  Mirer. — 
Figure  23  shows  the  construc- 
tion of  one  of  the  best  known 
makes  of  gravity  mixers  of 
the  trough  form.  In  operation 
the  cement,  sand  and  stone  in 
the  proper  proportions  are 
spread  in  superimposed  layers 
on  a  shoveling  board  at  hop- 
per level  and  are  then  shov- 
eled as  evenly  as  possible  into 
the  hopper.  From  the  hopper 
the  materials  flow  down  the 
trough,  receiving  the  water 
about  half  way  down,  and  are 
mixed  by  being  cut  and  turned 
by  the  pins  and  deflectors.  The 
trough  of  the  mixer  is  about 
10  ft.  long. 

Hains  Gravity  Mirer. — The 
form  of  gravity  mixer  made  by 
the  Hains  Concrete  Mixer  Co., 
Washington,  T).  C.,  is  shown 
by  Figs.  24  and  25.  The  charge 
passes  through  the  hoppers  in 
succession.  Considering  first 
the  stationary  plant,  shown  by 
Fig.  24,  the  four  hoppers  at 
the  top  have  a  combined  ca- 
pacity of  one  of  the  lower  hop- 
pers. Each  top  hopper  is  charged  with  cement,  sand  and 
stone  in  the  order  named  and  in  the  proper  proportions. 
Water  is  then  dashed  over  the  tops  of  the  filled  hoppers 
and  they  are  dumped  simultaneously  into  the  hopper 


Fig.    2?>. — Gilbreth   Gravity 
Mixer,    Trough    Form. 


MACHINE   MIXING. 


81 


next  below.  This  hopper  is  then  discharged  into  the 
next  and  so  on  to  the  bottom.  Meanwhile  the  four  top  hop- 
pers have  been  charged  with  materials  for  another  batch.  It 
will  be  observed  that  (i)  the  concrete  is  mixed  in  separate 
batches  and  (2)  the  ingredients  making  a  batch  are  accurately 
proportioned  and  begin  to  be  mixed  for  the  whole  batch  at 

Storage  Bin 


j        Stone 

Sand 

Stone 

t 

I 

i 

! 

i 

! 

ri  v- 

*•  ZA?0r  -"       t 

$                 1 

! 

Four  Men  are  stationed  on  this  Platform  one 


Cement  delivered  to 
this  Platform 

— ...JZL^J 


Side      Elevoi-fion . 
Fig.  24.— Hains  Gravity  Mixer,  Fixed  Hopper  Form. 

once.  The  best  arrangement  is  to  have  the  top  of  the  hopper 
tower  carry  sand  and  stone  bins  which  chute  directly  into  the 
top  hoppers.  In  the  telescopic  mixer  shown  by  Fig.  25  the 
purpose  has  been  to  provide  a  mixer  which,  hung  from  a 
derrick  or  cableway,  will  receive  a  charge  of  raw  materials 


82 


CONCRETE    CONSTRUCTION. 


at  stock  pile  and  deliver  a  batch  of  mixed  concrete  to  the 
work,  the  operation  of  mixing  being  performed  during  the 
hoist  to  the  work.  By  providing  two  mixers  so  that  one  can 
be  charged  while  the  other  is  being  hoisted  continuous  opera- 
tion is  secured.  The  following  are  records  of  operation  of  sta- 
tionary gravity  mixers  of  this  type. 

In  building  a  dock  at  Baltimore,  Md.,  a  plant  consisting  of 
two  large  hoppers  and  four  charging  hoppers  with  sand  and 
stone  bins  above  was  used.  One  man  at  each  large  conical 
hopper  tending  the  gates  and  two  men  charging  the  four 
pyramidal  hoppers  composed  the  mixer  gang.  A  scow  load  of 


Fig.  25. — Hains  Gravity  Mixer,  Telescoping  Hopper  Form. 

sand  and  another  of  stone  were  moored  alongside  the  work 
and  a  clam-shell  bucket  dredge  loaded  the  material  from  these 
barges  into  the  mixer  bins.  Each  batch  was  25  cu.  ft.  of  1-2-5 
concrete  rammed  in  place.  The  men  at  the  upper  hoppers 
would  empty  a  sack  of  cement  in  each,  and  then  by  opening 
gates  in  the  bottom  of  the  bins  above,  allow  the  necessary 
amounts  of  sand  and  stone  to  flow  in,  marks  having  been 
previously  made  on  the  sides  of  the  hoppers  to  show  the  cor- 
rect proportion  of  each  of  the  ingredients.  The  amount  of 


MACHINE   MIXING.  83 

water  found  by  experience  to  be  necessary,  would  then 
be  dashed  into  the  hoppers,  and  the  charges  allowed  to  run 
into  the  first  cone  hopper  below.  Refilling  would  begin  at  the 
top  white  the  men  were  caring  for  the  first  charge  in  the 
lower  hoppers.  The  process  was  thus  continuous.  The  con- 
crete was  chuted  directly  into  place  from  the  bottom  hopper. 
The  record  of  output  was  no  batches  per  lo-hour  day.  Wages 
of  common  labor  were  $1.50  per  day.  The  labor  cost  per  cubic 
yard  of  concrete  in  place  was  35  cts. 

In  constructing  the  Cedar  Grove  reservoir  at  Newark,  N.  J.. 
a  Hains  mixer  made  the  following  records  of  output : 

Cu.  yds. 

Best   output  per    zo-hour   day    403 

Average  daily  output  for  best  month   302 

Average  daily  output  for  whole  job   225 

The  stone,  sand  and  cement  were  all  raised  by  bucket  ele- 
vators to  the  top  of  the  high  wooden,  tower  that  supported  the 
bins  and  mixer.  There  were  10  men  operating  the  mixer  so 
that  (exclusive  of  power,  interest  and  depreciation)  the  labor 
cost  of  mixing  averaged  only  7  cts.  per  cu.  yd. ;  during  one 
month  it  was  as  low  as  5  cts.  per  cu.  yd.  This  does  not  in- 
clude delivering  the  materials  to  the  men  at  the  mixer,  nor 
does  it  include  conveying  the  concrete  away  and  placing  it. 
The  work  was  done  by  contract. 

OUTPUT  OF  MIXERS.— With  a  good  mixer  the  output 
depends  upon  the  methods  of  conveying  the  materials  to  and 
from  the  mixer.  Most  makers  of  mixers  publish  capacities  of 
their  machines  in  batches  or  cubic  yards  output  per  hour; 
these  figures  may  generally  be  taken  as  stating  nearly  the 
maximum  output  possible.  Considering  batch  mixers,  as 
being  the  type  most  commonly  used,  it  may  be  assumed  that 
where  the  work  is  well  organized  and  no  delay  occurs  in  de- 
livering the  materials  to  the  mixer  that  a  batch  every  2  min- 
utes, or  300  batches  in  10  hours,  will  be  averaged,  and  there 
are  a  few  records  of  a  batch  every  il/2  minutes. 

To  illustrate  to  how  great  an  extent  the  output  of  a  mixer 
depends  on  the  methods  adopted  in  handling  the  materials 
to  and  from  the  mixer  we  compare ^two  actual  cases  that  came 
under  the  authors'  observation.  The  mixers  used  were  of 
the  same  size  and  make.  In  one  case  the  stone  was  shoveled 


84  CONCRETE    CONSTRUCTION. 

into  the  charging  hopper  by  four  men  and  the  sand  and  cement 
were  delivered  in  barrows  by  four  other  men ;  six  men  took 
the  concrete  away  in  wheelbarrows.  The  output  of  the  mixer 
was  one  batch  every  5  minutes,  or  120  batches,  or  60  cu.  yds., 
in  10  hours.  In  the  other  case  the  sand  and  the  stone  were 
chtited  directly  into  the  charging  hopper  from  overhead  bins 
and  the  mixer  discharged  into  one-batch  buckets  on  cars.  The 
output  of  the  mixer 'was  one  batch  every  2  minutes,  or  300 
batches  in  10  hours.  In  the  first  case  the  capacity  of  the 
mixer  was  limited  by  the  ability  of  a  gang  of  workable  size 
to  get  the  raw  materials  to  and  the  mixed  concrete  away 
from  the  mixer.  In  the  second  case  the  capacity  was  limited 
only  by  the  amount  of  mixing  deemed  necessarv. 

While  the  necessity  of  rapid  charging  of  a  mixer  to  secure 
its  best  output  is  generally  realized  it  is  often  forgotten  that 
the  rapidity  of  discharge  is  also  a  factor  of  importance.  The 
size  of  the  conveyor  by  which  the  concrete  is  removed  affects 
the  time  of  discharge.  By  timing  a  string  of  wheelbarrows 
in  line  the  authors  have  found  that  it  takes  about  7  seconds  to 
fill  each  barrow ;  as  a  rule  slight  delays  will  increase  this 
time  to  10  seconds.  With  a  load  of  i  cu.  ft.  per  barrow  it 
requires  13  barrow  loads  to  take  away  a  y2  cu.  yd.  batch. 
This  makes  the  time  of  discharging  a  batch  130  seconds,  or 
say  2  minutes.  The  same  mixer  discharging  into  a  batch  size 
bucket  will  discharge  in  15  to  20  seconds,  saving  at  least  \l/> 
minutes  in  discharging  each  batch. 

MIXER  EFFICIENCY.— Various  attempts  have  been 
made  to  late  the  efficiency  of  concrete  mixers.  In  all  cases 
a  percentage  basis  of  comparison  has  been  adopted ;  arbitrary 
values  are  assigned  to  the  several  functions  of  a  mixer,  such 
as  40  per  cent,  for  perfect  mixing,  10  per  cent,  for  time  of 
mixing  and  25  per  cent,  for  control  of  water,  the  total  being 
100  per  cent.,  and  each  mixer  analyzed  and  given  a  rating 
according  as  it  is  considered  to  approach  the  full  value  of  any 
function.  Such  percentage  ratings  are  unscientific  and  mis- 
leading; they  present  definite  figures  for  what  are  mere 
arbitrary  determinations.  The  values  assigned  to  the  several 
functions  are  purely  arbitrary  in  the  first  place,  and  in  the 
second  place  the  decision  as  to  how  near  those  values  any 
mixer  approaches  are  matters  of  personal  judgment. 


MACHINE   MIXING.  85 

The  most  efficient  mixer  is  the  one  that  gives  the  maximum 
product  of  standard  quality  at  the  least  cost  for  production. 

This  rule  recognizes  the  fact  that  in  practical  construction 
different  standards  of  quality  are  accepted  for  different  kinds 
of  work.  No  engineer  demands,  for  example,  the  same  quality 
of  mixture  for  a  pavement  base  that  he  does  for  a  reinforced 
concrete  girder.  If  mixer  A  turns  out  concrete  of  a  quality 
suitable  for  pavement  base  cheaper  than  does  mixer  B,  then  it 
is  the  more  efficient  mixer  for  the  purpose,  even  though  mixer 
B  will  make  the  superior  quality  of  concrete  required  for  a 
reinforced  girder  while  mixer  A  will  not.  This  method  of  de- 
termining efficiency  holds  accurate  for  any  standard  of  quality 
that  may  be  demanded. 


CHAPTER  V. 

METHODS  AND  COST  OF  DEPOSITING  CONCRETE 

UNDER  WATER  AND  OF  SUBAQUEOUS 

GROUTING. 

Mixed  concrete  if  emptied  loose  and  allowed  to  sink  through 
water  is  destroyed ;  the  cement  paste  is  washed  away  and  the 
sand  and  stone  settle  onto  the  bottom  more  or  less  seggre- 
gated  and  practically  without  cementing  value.  In  fact,  if 
concrete  is  deposited  with  the  utmost  care  in  closed  buckets 
and  there  is  any  current  to  speak  of  a  considerable  portion  of 
cement  is  certain  to  wash  out  of  the  deposited  mass.  Even 
in  almost  still  water  some  of  the  cement  will  rise  to  the  sur- 
face and  appear  as  a  sort  of  milky  scum,  commonly  called 
hiitancc.  Placing  concrete  under  water,  therefore,  involves 
the  distinctive  task  of  providing  means  to  prevent  the  wash- 
ing action  of  the  water.  It  is  also  distinguished  from  work 
done  in  air  by  the  fact  that  it  cannot  be  compacted  by  ram- 
ming, but  the  main  problem  is  that  of  preventing  wash  dur- 
ing and  after  placing. 

DEPOSITING  IN  CLOSED  BUCKETS.— Special  buckets 
for  depositing  concrete  under  water  are  made  by  several  man- 
ufacturers of  concrete  buckets.  These  buckets  vary  in  detail 
but  are  all  similar  in  having  doors  to  close  the  concrete  away 
from  the  water  and,  generally,  in  being  bottom  dumping. 

The  bucket  shown  by  Fig.  26  was  designed  by  Mr.  John 
F.  O'Rourke,  and  is  built  by  the  Cockburn  Barrow  &  Ma- 
chine Co.,  of  Jersey  City,  N.  J.  This  bucket  was  used  in  de- 
positing the  concrete  for  the  City  Island  Bridge  foundations 
described  in  Chapter  XII  and  also  in  a  number  of  other  works. 
It  consists  of  a  nearly  cubical  shell  of  steel  open  at  top  and 
bottom,  and  having  heavy  timbers  rivetted  around  the  bottom 
edges.  The  open  top  has  two  flat  flap  doors.  Two  similar 
doors  hinged  about  midway  of  the  sides  close  to  form  a  V- 
shaped  hopper  bottom  inside  the  shell  and  serve  when  open,  to 

86 


SUBAQUEOUS   CONCRETING.  87 

close  the  openings  in  the  sides  of  the  shell.  In  loading  the 
bucket  the  bottom  doors  are  drawn  inward  and  upward  by 
the  chains  and  held  by  a  temporary  key.  The  loaded  bucket 
is  tjien  lifted  by  the  bail  and  the  key  removed,  since  when 
suspended  the  pull  on  the  bail  holds  the  chains  taut  and  the 
doors  closed.  As  soon  as  the  bucket  rests  on  the  bottom  the 
pull  of  the  concrete  on  the  doors  slides  the  bail  down  and  the 
doors  swing  downward  and  back  discharging  the  concrete. 
The  timbers  around  the  bottom  edges  keep  the  bucket  from 
sinking  into  the  deposited  concrete,  and  the  doors  and  shell 
exclude  all  water  from  the  batch  until  it  is  finally  in  place. 


Fig.    26.— O'Rourke    Bucket    fur    Depositing    Concrete    Under    Water. 

The  subaqueous  concrete  bucket  shown  by  Figs.  27  and  28 
is  made  by  the  Cyclopean  Iron  Works 'Co.,  Jersey  City,  N.  J. 
Fig.  27  shows  the  bucket  suspended  full  ready  for  lowering; 
the  cover  is  closed  and  latched  and  the  bail  is  held  vertical  by 
the  tag  line  catch  A.  Other  points  to  be  noted  are  the  eccen- 
tric pivoting  of  the  bail,  the  latch  unlocking  lever  and  roller 
B  and  C,  and  the  stop  D.  In  the  position  shown  the  bucket 
is  lowered  through  the  water  and  when  at  the  proper  depth 
just  above  bottom  the  tag  line  is  given  a  sharp  pull,  uneaten- 
ing  the  bail.  The  body  of  the  bucket  turns  bottom  side  up, 


88 


CONCRETE    CONSTRUCTION. 


revolving  on  the  bail  pivots,  and  just  as  the  revolution  is  com- 
pleted the  bail  engages  the  roller  C  on  the  latch  unlocking 
lever  and  swings  the  lever  enough  to  unlatch  the  top  and  al- 
low it  to  swing  down  as  shown  by  Fig.  28  and  release  the  con- 
crete. The  stop  D  keeps  the  body  of  the  bucket  from  swing- 
ing beyond  the  vertical  in  dumping. 


Fig.    21. — Cyclopean    Bucket    for 

Depositing   Concrete    Under 

Water    (Closed 

Position). 


Fig.    28. — Cyclopean    Bucket    for 
Depositing    Concrete    Under 
Water    (Open 
Position). 


Figures  29  and  30  show  the  subaqueous  concrete  bucket 
made  by  the  G.  L.  Stuebner  Iron  Works,  Long  Island  City, 
N.  Y. ,  essentially  the  same  bucket,  omitting  the  cover  and 
with  a  peaked  bail,  is  used  for  work  in  air.  For  subaqueous 
work  the  safety  hooks  A  are  lifted  from  the  angles  B  and 
wired  to  the  bail  in  the  position  shown  by  the  dotted  lines,  and 
a  tag  line  is  attached  to  the  handle  bar  C.  The  bucket  being 
filled  and  the  cover  placed  is  lowered  through  the  water  to  the 
bottom  and  then  discharged  by  a  pull  on  the  tag  line. 


SUBAQUEOUS   CONCRETING.  89 

DEPOSITING  IN  BAGS.— Two  methods  of  depositing, 
concrete  in  bags  are  available  to  the  engineer ;  one  method  is 
to  employ  a  bag  of  heavy  tight  woven  material,  from  which 
the  concrete  is  emptied  at  the  bottom,  the  bag  serving  like  the 
buckets  previously  described  simply  as  means  of  conveyance, 
and  the  other  method  is  to  use  bags  of  paper  or  loose  woven 
gunnysack  which  are  left  in  the  work,  the  idea  being  that  the 
paper  will  soften  or  the  cement  will  ooze  out  through  the 
openings  in  the  cloth  sufficiently  to  bond  the  separate  bagfuls 
into  a  practically  solid  mass. 


Fig.    29. — Stuebner    Bucket    I'or 
Depositing    Concrete    Under 
Water    (Closed 
Position). 


Fig.    30.— Stuebner    Bucket    for 

Depositing    Concrete    Under 

Water   (Open 

Position). 


The  bag  shown  by  Fig.  31  was  used  to  deposit  concrete 
for  leveling  up  a  rough  rock  bottom  and  so  provide  a  footing 
for  a  concrete  block  pier  constructed  in  1902  at  Peterhead, 
N.  B.,  by  Mr.  William  Shield,  M.  Inst.  C.  E.  Careful  longi- 
tudinal profiles  were  taken  of  the  rock  bottom  one  at  each 
edge  of  the  footing.  Side  forms  were  then  made  in  2O-ft. 
sections  as  shown  by  Fig.  32;  the  lagging  boards  being  cut  to 
fit  the  determined  profile  and  the  top  of  the  longitudinal  piece 
being  flush  with  the  top  of  the  proposed  footing.  The  con- 
crete was- filled  in  between  the  side  forms  and  leveled  off  by 
the  T-rail  straightedge.  In  placing  the  side  forms  the  long- 
itudinal pieces  were  placed  by  divers  who  were  given  the 
proper  elevations  by  level  rods  having  10  to  15-ft.  extension 


90  CONCRETE    CONSTRUCTION. 

pieces  to  raise  the  targets  above  the  water  surface.  When 
leveled  the  side  pieces  were  anchor-bolted  as  shown  to  the 
rock,  the  anchor-bolts  being  wedged  into  the  holes  to  permit 
future  removal.  The  concrete  was  then  lowered  in  the  bag 


Line  for 
LoweringBag 


Fig.   31. — Bag  for  Depositing  Concrete  Under  Water. 

shown  by  Fig.  31,  the  divers  assisting  in  guiding  the  bag  to 
position.  The  mouth  of  the  bag  being  tied  by  one  turn  of  a 
line  having  loops  through  which  a  wooden  key  is  slipped  to 
hold  the  line  tight,  a  sharp  tug  on  the  tripping  rope  loosens 


ail  Straight  ILolqe  -^ 


v 

$ 

ij 

Cj-T- 

;; 

11 

T~- 

j 

4* 

pj^ 

'• 

^ 

'~>>. 

Tl* 

1 

"^ 

— 

$n 

li 

rr^,/^"          || 

Li 

Fig.  32.— Form  for  Molding    Footing  for  Block  Concrete  Breakwater. 

the  key  and  empties  the  bag.  The  bags  used  on  this  work  had 
a  capacity  of  2l/4  cu.  ft.  To  permit  the  removal  of  the  side 
forms  after  the  concrete  had  hardened,  a  strip  of  jute  sacking 
was  spread  against  the  lagging  boards  with  a  flap  extending 


SUBAQUEOUS   CONCRETING. 


7 


----X 


15  to  18  ins.  under  the  concrete.    The  forms  were  removed  by 

divers  who  loosened  the  anchor  bolt  wedges. 

In  placing  small  amounts  of  concrete  for  bridge  foundations 
in  Nova  Scotia,  bags,  made  of  rough 
brown  paper  were  used  to  hold  the  con- 
crete. Each  bag  held  about  i  cu.  ft.  The 
bags  were  made  up  quickly  and  dropped 
into  the  water  one  after  the  other  so  that 
the  following  one  was  deposited  before 
the  cement  escaped  from  the  former  one. 
The  paper  was  immediately  destroyed  by 
submersion  and  concrete  remained.  The 
bags  cost  $1.35  per  hundred  or  35  cts.  per 
cu.  yd.  of  concrete.  Concrete  was  thus 
deposited  in  18  ft.  of.  water  without  a 
diver. 

DEPOSITING  THROUGH  A 
TREMIE. — A  tremie  consists  of  a  tube 
of  wood  or,  better,  of  sheet  metal,  which 
reaches  from  above  the  surface  to  the 
bottom  of  the  water ;  it  is  operated  by  fill- 
ing the  tube  with  concrete  and  keeping  it 
full  by  successive  additions  while  allow- 
ing the  concrete  to  flow  out  gradually  at 
the  bottom  by  raising  the  tube  slightly  to 
provide  the  necessary  opening.  A  good 
example  of  a  sheet  steel  tremie  is  shown 
by  Fig.  33.  This  tremie  was  used  by  Mr. 
Wm.  H.  Ward  in  constructing  the  Har- 
vard Bridge  foundations  and  numerous 
other  subaqueous  structures  of  concrete. 
In  these  works  the  tube  was  suspended 
from  a  derrick.  Wheelbarrows  filled  the 
tube  and  hopper  with  concrete  and  kept 
-Fig.  33.-steei  Tremie  them  full;  the  derrick  raised  the  tube  a 
«or  Depositing  Concrete  few  inches  and  swung  it  gently  so  ab  to 

Under  Water.  .    .A   _,_.!„  Qver  t|ie  area  to  be  filled, 


»  &***&&> 


Care  being  taken  to  keep  the  tube  at  one  height,  the  concrete 
was  readily  deposited  in  even  layers.    Concrete  thus  deposited 


92 


CONCRETE    CONSTRUCTION. 


in  18  ft.  of  water  was  found  to  be  level  and  solid  on  pumping 
the  pit  dry. 

Another  method  of  handling  a  tremie  was  employed  in  con 
structing  the  foundations  for  the  Charlestown  Bridge  at  Bos- 
ton, Mass.  Foundation  piles  were  driven  and  sawed  off  under 
water.  A  frame  was  built  above  water  and  supported  by  a 
curbing  attached  to  certain  piles  in  the  outer  rows  of  the 
foundation  reserved  for  this  purpose.  In  this  frame  the  verti- 
cal members  were  Wakefield  sheet-piling  plank,  spaced  6  to 
10  ft.  apart,  and  connected  by  three  lines  of  double  waling 


Fig.  34.— Tremie  and  Traveler  Used  at  Charlestown,  Mas?...  Bridge. 

bolted  to  the  verticals  at  three  different  heights.  This  frame 
was  lowered  to  the  bottom  so  as  to  enclose  the  bearing  piles. 
The  posts  or  verticals  were  then  driven,  one  by  one,  into  the 
bottom,  the  frame  being  flexible  enough  to  permit  this.  The 
spaces  between  the  posts  or  verticals  were  then  rilled  by  sheet- 
piling  and  the  frame  was  bolted  to  the  curbing  piles.  This 
curbing  afterward  supported  the  traveler  used  in  laying  the 
concrete.  Thus  a  coffer  dam  was  formed  to  receive  the  con- 
crete as  shown  in  Fig.  34.  The  1-2-5  concrete  was  de- 
posited up  to  within  5^  ft.  of  the  mean  low  water  level,  the 


SUBAQUEOUS   CONCRETING. 


93 


last  foot  being  laid  after  water  was  pumped  out.  The  tremie 
used  to  deposit  the  concrete  was  a  tube  14  ins.  in.  diameter  at 
the  bottom  and  1 1  ins.  at  the  neck,  with  a  hopper  at  the  top. 
It  was  made  in  removable  sections,  with  outside  flanges,  and 
was  suspended  by  a  differential  hoist  from  a  truck  moving 
laterally  on  a  traveler,  Fig.  34.  The  foot  of  the  chute  rested 
on  the  bottom  until  filled  with  concrete ;  then  the  chute  was 
slowly  raised  and  the  concrete  allowed  to  run  out  into  a 
conical  heap,  more  concrete  being  dumped  into  the  hopper. 
As  the  truck  moved  across  the  traveler  a  ridge  of  concrete 
was  made ;  then  the  traveler  was  moved  forward  and  another 
parallel  ridge  was  made.  The  best  results  were  obtained  when 
the  layers  were  2]/2  ft.  thick,  but  layers  up  to  6  ft.  thick  were 
laid.  If  the  layer  was  too  thick,  or  uneven,  or  if  the  chute  was 
moved  or  raised  too  quickly,  the  charge  in  the  tube  was  "lost." 
This  was  objectionable  because  the  charging  of  the  chute 
anew  resulted  in  "washing"  the  cement  more  or  less  out  of  the 
concrete  until  the  chute  was  again  filled.  To  reduce  this  ob- 
jection the  contractor  was  directed  to  dump  some  neat  cement 
into  the  tube  before  filling  with  concrete.  A  canvass  piston 
was  devised  which  could  be  pushed  ahead  of  the  concrete 
when  filling  the  chute.  It  consisted  of  two  truncated  cones 
of  canvass,  one  flaring  downward  to  force  the  water  ahead, 
and  the  other  flaring  upward  to  hold  the  concrete.  The  can- 
vass was  stiffened  and  held  against  the  sides  of  the  chute  by 
longitudinal  ribs  of  spring  steel  wire;  the  waist  was  filled  by 
a  thick  block  of  wood  to  which  all  the  springs  were  attached; 
and  to  this  block  were  connected  additional  steel  guides  to 
prevent  overturning  and  a  rope  to  regulate  the  descent.  Very 
little  water  forced  its  way  past  this  piston  and  it  was  a  suc- 
cess, but  as  the  cost  was  considerable  and  a  piston  was  lost 
each  time,  its  use  was  abandoned  as  the  evil  to  be  avoided  did 
not  justify  the  outlay. 

The  chute  worked  best  when  the  concrete  was  mixed  not 
quite  wet  enough  to  be  plastic.  If  mixed  too  wet  the  charge 
was  liable  to  be  "lost,"  and  if  dry  it  would  choke  the  chute. 
An  excess  of  gravel  permitted  water  to  ascend  in  the  tube; 
and  an  excess  of  sand  tended  to  check  the  flow  nf  concrete. 

In  constructing  the  piers  for  a  masonry  arch  bridge  in 
France  in  1888  much  the  same  method  was  followed,  except 


94 


CONCRETE    CONSTRUCTION. 


that  a  wooden  tremie  16  ins.  square  made  in  detachable  sec- 
tions was  used.  This  tremie  had  a  hopper  top  and  was  also 
provided  with  a  removable  cap  or  cover  for  the  bottom  end, 
the  latter  device  being  intended  to  keep  the  water  out  of  the 
tube  and  prevent  "washing"  the  first  charge  of  concrete.  The 
piers  were  constructed  by  first  driving  piles  and  sawing  them 
off  several  feet  above  the  bottom  but  below  wrater  level,  and 
then  filling  them  nearly  to  their  tops  with  broken  stone.  An 
open  box  caisson  'was  then  sunk  onto  the  stone  and  embrac- 
ing the  pile  tops  and  then  filled  around  the  outside  with  more 
broken  stone.  The  caisson  was  then  filled  with  concrete 
through  the  tremie  which  was  handled  by  a  traveling  crane. 
The  crane  was  mounted  and  traveled  transversely  of  the  pier 
on  a  platform  which  in  turn  moved  along  tracks  laid  length- 
wise of  the  caisson.  The  tube  was  gradually  filled  with  con- 
crete and  lowered,  the  detachable  bottom  of  the  tube  was  then 
removed,  allowing  the  concrete  to  run  out.  The  tube  was 
first  moved  across  the  caisson  and  then  down-stream  and  back 
across  the  caisson,  and  this  operation  repeated  until  a  i6-in. 
layer  was  completed.  The  tube  was  then  raised  16  ins.  and 
the  operations  repeated  to  form  another  layer.  There  was 
almost  no  laitancc.  From  90  to  100  cu.  yds.  were  deposited 
daily. 

Still  another  example  of  tremie  work  is  furnished  by  the 
task  of  depositing  a  large  mass  of  concrete  under  water  in  the 
construction  of  the  Nussdorf  Lock  at  Vienna.  This  lock  has  a 
total  width  of  92  ft.  over  all,  and  is  49.2  ft.  clear  inside.  The 
excavation,  which  was  carried  to  a  depth  of  26.24  ft.  below 
water  level,  was  made  full  width,  between  sheet  piling,  and 
the  bottom  was  filled  in  with  rammed  sand  and  gravel,  form- 
ing a  kind  of  invert  with  its  upper  surface  horizontal  in  the 
middle  and  sloping  upwards  a  trifle  at  both  sides.  A  mass  of 
concrete  having  a  total  thickness  of  13.12  ft.  was  built  on  this 
foundation  in  the  center  where  the  upper  surfaces  were  13.12 
ft.  below  the  water  level.  Concrete  walls  were  carried  up  at 
the  sides  of  the  lock  to  a  height  of  3.28  ft. ;  these  walls  were 
8.2  ft.  thick.  The  methods  used  in  placing  the  concrete  were 
as  follows :  Three  longitudinal  rows  of  piles  were  driven  on 
each  side  of  the  axis  of  the  lock,  these  piles  supporting  a  6-rail 
track  about  7  ft.  above  the  water  level.  Three  carriages  span- 


SUBAQUEOUS   CONCRETING.  95 

ning  the  full  width  of  the  lock  transversely  moved  on  this 
track.  Each  carriage  had  three  trolleys,  one  in  each  of  the 
main  panels  of  the  transverse  pile  bends.  These  trolleys  each 
carried  a  vertical  telescopic  tube,  by  means  of  which  the  con- 
crete was  deposited  at  the  bottom  of  the  lock.  These  tubes 
or  chutes  were  of  different  lengths  in  the  three  carriages ;  the 
first  ones  deposited  the  concrete  up  to  a  level  of  23  ft.  below 
the  surface ;  the  next  set  deposited  the  concrete  between  that 
level  and  19.7  ft.,  and  the  last  set  completed  the  subaqueous 
work  up  to  the  final  height  of  16.4  ft.  below  the  surface.  The 
tops  of  the  tubes  were  level  with  a  transverse  track  extending 
the  full  length  of  the  carriage.  The  ends  of  these  tfacks  just 
cleared  the  outside  rows  of  piles,  which,  on  one  side  of  the 
lock,  supported  a  distribution  track  parallel  to  the  axis  of  the 
lock.  Dump  cars  running  on  this  distribution  track  delivered 
the  concrete  to  smaller  dump  cars  on  the  carriage  tracks,  and 
in  turn  these  smaller  cars  dumped  into  either  of  these  chutes 
on  each  carriage.  The  carriages  were  moved  from  end  to  end 
of  the  lock,  the  whole  area  of  the  lock  coming  under  the  nine 
chutes,  inasmuch  as  each  chute  moved  one-third  the  length  of 
the  carriage.  The  concrete  was  deposited  in  three  horizontal 
layers  3.28  ft.  thick,  the  layers  being  built  in  comparatively 
narrow  banks,  so  that  the  different  layers  would  key  together 
and  form  a  corrugated  mass.  The  chutes  were  shortened  as 
the  concrete  was  deposited,  three  layers  being  placed  succes- 
sively. The  main  body  of  the  bottom  and  the  side  walls  were 
built  by  this  method,  and  then  the  water  was  pumped  out  and 
a  2.3  ft.  layer  of  concrete  rammed  over  the  bottom  and  com- 
pleted with  a  finished  surface  9  ft.  thick. 

GROUTING  SUBMERGED  STONE.— Masses  of  gravel, 
broken  or  rubble  stone  deposited  under  water  may  be  ce- 
mented into  virtually  a  solid  concrete  by  charging  the  inter- 
stices with  grout  forced  through  pipes  from  the  surface.  Mr. 
H.  F.  White  gives  the  following  records  of  grouting  sub- 
merged gravel : 

In  experiment  No.  I  a  reservoir  10  ft.  square  was  filled  to 
a  depth  of  18  ins.  with  clean  gravel  ballast  (il/2  to  2-in.  size) 
submerged  in  water.  A  2-in.  gas  pipe  rested  on  the  gravel 
and  was  surmounted  with  a  funnel.  A  i  :i  Portland  grout 
was  poured  in.  After  21  days  set  the  water  was  drawn  off, 


96  CONCRETE    CONSTRUCTION. 

and  it  was  found  that  the  grout  had  permeated  the  ballast  for 
a  space  of  8  ft.  square  at  the  bottom  and  6  ft.  square  at  the  top, 
leaving  a  small  pile  of  pure  cement  mortar  6  ins.  high  about 
the  base  of  the  pipe;  16  cu.  ft.  of  cement  and  16  cu.  ft.  of  sand 
concreted  100  cu.  yds.  of  ballast.  In  experiment  No.  2,  under 
the  same,  conditions,  a  grout  made  of  I  part  lime,  i  part  surki 
(puzzulana  or  trass)  and  i  part  sand,  was  found  to  have 
spread  over  the  entire  bottom,  10  ft.  square,  rising  5  ins.  on  the 
sides,  and  making  the  concreted  mass  about  3^/2  ft.  square  at 
the  top;  25  cu.  ft.  of  the  dry  materials  concreted  100  cu.  ft.  of 
ballast.  In  experiment  No.  3  the  ballast  was  2J/2  ft.  deep.  A 
grout  (using  8  cu.  ft.  of  each  ingredient)  made  as  in  experi- 
ment No.  2  covered  the  bottom,  rose  14  ins.  on  the  sides  and 
made  a  top  surface  4^2  ft.  square ;  32  cu.  ft.  of  the  dry  mate- 
rials grouted  100  cu.  ft.  of  ballast.  In  experiment  No.  4  the 
ballast  was  of  bats  and  pieces  3  or  4  ins.  in  size  laid  7  ft.  deep. 
A  grout  made  as  in  experiment  No.  2  (using  88  cu.  ft.  of  each 
ingredient)  concreted  the  whole  mass  to  a  depth  of  6  ft.  up  the 
sides,  and  2^/2  ft.  square  at  the  pipe  on  the  surface  of  the  bal- 
last. Mr.  White  says  that  a  grout  containing  more  than  i 
part  of  sand  to  i  of  Portland  cement  will  not  run  freely 
through  a  2-in.  pipe,  as  the  sand  settles  out  and  chokes  the 
pipe.  Even  with  i  :i  grout  it  must  be  constantly  stirred  and  a 
steady  flow  into  the  pipe  maintained.  The  lime-trass  grout 
does  not  give  the  same  trouble. 

Mr.  W.  R.  Knipple  describes  the  work  of  grouting  rubble 
stone  and  gravel  for  the  base  of  the  Hermitage  Breakwater. 
This  breakwater  is  525  ft.  long,  50  ft.  wide  at  base  and  42  ft. 
wide  at  top,  and  68  ft.  high,  was  built  on  the  island  of  Jersey. 
Where  earth  (from  o  to  8^  ft.  deep)  overlaid  the  granite  rock, 
it  was  dredged  and  the  trench  filled  in  with  rubble  stones  and 
gravel  until  a  level  foundation  was  secured.  Cement  grout 
was  then  forced  into  this  filling  through  pipe  placed  8  to  TO  ft. 
apart.  The  grouting  was  done  in  sections  T2j/£  ft.  long,  from 
7  to  10  days  being  taken  to  complete  each.  Upon  this  foun- 
dation concrete  blocks,  4x4x9  to  12  ft.,  were  laid  in  courses 
inclined  at  an  angle  of  68°.  The  first  four  courses  were  laid 
by  divers,  the  blocks  being  stacked  dry  two  courses  high  at  a 
time.  The  joints  below  water  were  calked  by  divers  and  above 
water  by  masons,  and  a  section  was  then  grouted.  When  two 


SUBAQUEOUS   CONCRETING.  97 

courses  had  been  laid  and  grouted,  two  more  courses  were 
laid  and  grouted  in  turn,  and  so  on.  In  places,  grouting  was 
done  in  50  ft.  of  water.  The  grout  should  be  a  thick  paste; 
a  3O-ft.  column  of  grout  will  balance  a  6o-ft.  column  of  water. 


CHAPTER  VI. 

METHODS    AND    COST    OF    MAKING    AND    USING 
RUBBLE  AND  ASPHALTIC  CONCRETE. 

Two  kinds  of  concrete  which  vary  in  composition  and  char- 
acter from  the  common  standard  mixtures  of  cement,  sand  and 
broken  aggregate  are  extensively  employed  in  engineering 
construction.  These  are  rubble  concrete  and  asphaltic  con- 
crete. 

RUBBLE  CONCRETE. — In  constructing  massive  walls 
and  slabs  a  reduction  in  cost  may  often  (not  always)  be  ob- 
tained by  introducing  large  stones  into  the  concrete.  Concrete 
of  this  character  is  called  rubble  concrete,  and  the  percentage 
of  rubble  stone  contained  varies  from  a  few  per  cent,  to,  in 
some  cases,  over  half  of  the  volume.  The  saving  effected 
comes  partly  from  the  reduction  in  the  cement  required  per 
cubic  yard  of  concrete  and  partly  from  the  saving  in  crushing. 

The  saving  in  cement  may  be  readily  figured  if  the  com- 
position of  the  concrete  and  the  volume  of  the  added  rubble 
stones  be  known.  A  1-2^-5  concrete  requires  according  to 
Table  X  in  Chapter  II  1.13  bbls.  of  cement  per  cubic  yard. 
Assuming  a  barrel  of  cement  to  make  3.65  cu.  ft.  of  paste,  we 
have  3.65  X  1.13  =  4.12  cu.  ft.  of  cement  paste  per  cubic  yard 
of  1-2^2-5  concrete.  This  means  that  about  15  per  cent,  of 
the  volume  of  the  concrete  structure  is  cement.  If  rubble 
stone  be  introduced  to  50  per  cent,  of  the  volume,  then  the 
structure  has  about  7^2  per  cent,  of  its  volume  of  cement.  It 
is  of  interest  to  note  in  this  connection  that  rubble  masonry 
composed  of  65  per  cent,  stone  and  35  per  cent,  of  1-2^2  mortar 
would  have  some  nl/2  per  cent,  of  its  volume  made  up  of  ce- 
ment. 

The  saving  in  crushing  is  not  so  simple  a  determination. 
Generally  speaking,  the  fact  that  a  considerable  volume  of  the 
concrete  is  composed  of  what,  we  will  call  uncrushed  stone, 
means  a  saving  in  the  stone  constituent  of  one  structure 

08 


RUBBLE   CONCRETE.  99 

amounting  to  what  it  would  have  cost  to  break  up  and  screen 
this  volume  of  uncrushed  stone,  but  there  are  exceptions.  For 
example,  the  anchorages  of  the  Manhattan  Bridge  over  the 
East  River  at  New  York  city  were  specified  to  be  of  rubble 
concrete,  doubtless  because  the  designer  believed  rubble  con- 
crete to  be  cheaper  than  plain  concrete.  In  this  case  an  eco- 
nomic mistake  was  made,  for  all  the  rubble  stone  used  had  to 
be  quarried  up  the  Hudson  River,  loaded  onto  and  shipped  by 
barges  to  the  site  and  then  unloaded  and  handled  to  the  work 
using  derricks.  Now  this  repeated  handling  of  large,  irreg- 
ular rubble  stones  is  expensive.  Crushed  stone  as  we  have 
shown  in  Chapter  IV  can  be  unloaded  from  boats  at  a  very 
low  cost  by  means  of  clam  shells.  It  can  be  transported  on  a 
belt  conveyor,  elevated  by  bucket  conveyer,  mixed  with  sand 
and  cement  and  delivered  to  the  work  all  with  very  little 
manual  labor  when  the  installation  of  a  very  efficient  plant  is 
justified  by  the  magnitude  of  the  job.  Large  rubble  stones 
cannot  be  handled  so  cheaply  or  with  so  great  rapidity  as 
crushed  stone ;  the  work  may  be  so  expensive,  due  to  repeated 
handlings,  as  to  offset  the  cost  of  crushing  as  well  as  the  extra 
cost  of  cement  in  plain  concrete.  On  the  other  hand-,  the  cost 
of  quarrying  rock  suitable  for  rubble  concrete  is  no  greater 
than  the  cost  of  quarrying  it  for  crushing — it  is  generally  less 
because  the  stone  does  not  have  to  be  broken  so  small — so  that 
when  the  cost  of  getting  the  quarried  rock  to  the  crusher  and 
the  crushed  stone  into  the  concrete  comes  about  the  same  as 
getting  the  quarried  stone  into  the  structure  it  is  absurd  prac- 
tice to  require  crushing.  To  go  back  then  to  our  first  thought, 
the  question  whether  or  not  saving  results  from  the  use  of 
rubble  concrete,  is  a  separate  problem  in  engineering  econom- 
ics for  each  structure. 

In  planning  rubble  concrete  work  the  form  of  the  rubble 
stones  as  they  come  from  the  quarry  deserves  consideration. 
Stones  that  have  flat  beds  like  many  sandstones  and  lime- 
stones can  be  laid  upon  layers  of  dry  concrete  and  have  the 
vertical  interstices  filled  with  dry  concrete  by  tamping.  It 
requires  a  sloppy  concrete  to  thoroughly  embed  stones  which 
break  out  irregularly.  In  the  following  examples  of  rubble 
concrete  work  the  reader  will  find  structures  varying  widely 


^^x 

OF  THE  A 

UNIVERSITY  1 

OF  7 


100 


CONCRETE    CONSTRUCTION. 


enough  in  character  and  in  the  percentages  of  rubble  used  to 
cover  most  ordinary  conditions  of  such  work. 

Where  the  rubble  stones  are  very  large  it  is  now  customary 
to  use  the  term  "cyclopean  masonry"  instead  of  rubble  con- 
crete. Many  engineers  who  have  not  studied  the  economics 
of  the  subject  believe  that  the  use  of  massive  blocks  of  stone 
bedded  in  concrete  necessarily  gives  the  cheapest  form  of 
masonry.  We  have  already  indicated  conditions  where  ordi- 
nary concrete  is  cheaper  than  rubble  concrete.  We  may  add 
that  if  the  quarry  yields  a  rock  that  breaks  up  naturally  into 
small  sized  blocks,  it  is  the  height  of  economic  folly  to  specify 
large  sized  cyclopean  blocks.  Nevertheless  this  blunder  has 
been  frequently  made  in  the  recent  past. 

Chattahoochee  River  Dam. — The  roll-way  portion,  680 
ft.  long,  of  the  dam  for  the  Atlanta  Water  &  Electric  Power 
Co.,  shown  in  section  by  Fig.  35,  was  built  of  a  heart- 


Fig.    35. — Diagram    Cross-Section    of   Rubble    Concrete    Dam,    Chattahoochee 

River. 

ing  of  rubble  concrete  with  a  fine  concrete  facing  and  a  rubble 
rear  wall.  The  facing,  12  ins.  thick  of  1-2-4  concrete,  gave  a 
smooth  surface  for  the  top  and  face  of  the  dam,  while  the 
rubble  rear  wall  enabled  back  forms  to  be  dispensed  with  and, 
it  was  considered,  made  a  more  impervious  masonry.  The 
concrete  matrix  for  the  core  was  a  1-2-5  stone  mixture  made 
very  wet.  The  rubble  stones,  some  as  large  as  4  cu.  yds., 
were  bedded  in  the  concrete  by  dropping  them  a  few  yards 
from  a  derrick  and  "working"  them  with  bars ;  a  well  formed 
stone  was  readily  settled  6  ins.  into  a  lo-in.  bed  of  concrete. 
The  volume  of  rubble  was  from  33  to  45  per  cent,  of  the  total 
volume  of  the  masonry.  The  1-2-4  concrete  facing  was 


RUBBLE   CONCRETE. 


101 


brought  up  together  with  the  rubble  core,  using  face  forms 
and  templates  to  get  the  proper  profile.  The  work  was  done 
by  contract  and  the  average  was  5,500  cu.  yds.  of  concrete 
placed  per  month. 

Barossa  Dam,  South  Australia.— The  Barossa  Dam  for  the 
water-works  for  Gawler,  South  Australia,  is  an  arch  with 
a  radius  of  200  ft.,  and  an  arc  length  on  top  of  422  ft. ;  its 


5trincf  course  of40-lb 
rail*  fi*hec*c*t joints- 

* 


sand 

434   "  cement 
^1  iff  n  _       7.ST%  excess  mortar 

Fig.  36.— Cross-Section  of    Barossa  Dam  of  Rubble  Concrete. 

height  above  the  bed  of  the  stream  is  95  ft.  Figure  36  is 
a  cross-section  of  the  dam  at  the  center.  The  dam  contains 
17,975  cu.  yds.  of  rubble  concrete  in  the  proportions  of  2,215 
cu.  yds.  of  rubble  stone  to  15,760  cu.  yds.  of  concrete;  thus 
about  12.3  per  cent,  of  the  dam  was  of  rubble.  The  concrete 
was  mixed  by  weight  of  I  part  cement,  \l/2  parts  sand,  and  a 
varying  proportion  of  aggregate  composed  of  4^  parts  \y\  to 


IO2 


CONCRETE    CONSTRUCTION. 


2-in.  stone,  2  parts  y2  to  i^-in.  stone  and  i  part  %  to  ^-in. 
stone  or  screenings.  The  sand  was  one-half  river  sand  and 
one-half  crusher  sand.  The  following  shows  the  amounts  by 
weight  of  the  several  materials  for  each  of  the  several  classes 
of  concrete  per  cubic  yard : 

Stone 


Class.    Excess  Mortar.    i%-2. 

A    7.5%         1,500 

B   12.5 

C 12.5  i,, 

D  15  1,402 


637 
637 
623 


Sand.    Cement. 
804 


884 


U. _......, 

!</5->H-J&'--->i  ! 


t£ 


d-Hon    of     Balance. 

l'|  \sl"Bearer  ..-•  3 Spreader 


E.N&.  NEWS, 


*^-*fz*4 


Plan  of  5alance. 

Fig.  37.— Apparatus  Used  for  Weighing  Concrete  Materials  at  Barossa  Dam. 

The  average  composition  of  the  concrete  was  1-1^-3^2.  Its 
cost  per  cubic  yard  in  place  including  rubble  was  383  Qd  per 
cu.  yd.  or  about  $9.30.  In  proportioning  the  mixture  on  the 
work  use  was  made  of  the  device  shown  by  Fig.  37  to  weigh 
the  aggregate.  The  measuring  car  is  pushed  back  under  the 
stone  hopper  chute  until  the  wheels  drop  into  shallow  notches 
in  the  balanced  track  rails;  stone  is  then  admitted  until  the 
lead  weight  begins  to  rise,  when  the  car  is  pushed  forward  and 
dumps  automatically 'as  indicated. 


RUBBLE   CONCRETE.  IC>3 

Other  Rubble  Concrete  Dams. — Rubble  concrete  contain- 
ing from  55  to  60  per  cent,  rubble  was  used  in  construct- 
ing the  Boonton  Dam  at  Boonton,  N.  J.  The  stones  used 
measured  from  I  to  2l/2  cu.  yds.  each ;  the  concrete  was 
made  so  wet  that  when  the  stones  were  dropped  into  it,  it 
flowed  into  every  crevice.  The  materials  were  all  delivered 
on  cars,  from  which  they  were  delivered  to  the  dam  by  der- 
ricks provided  with  bull-wheels.  On  the  dam  there  were  4 
laborers  and  I  mason  to  each  derrick,  and  this  gang  dumped 
the  concrete  and  joggled  the  rubble  stones  into  it.  Records 
of  125  cu.  yds.  per  10  hours,  with  one  derrick,  were  made. 
With  35  derricks,  20  of  which  were  laying  masonry  and  15 
either  passing  materials  or  being  moved,  as  much  as  21,000 
cu.  yds.  of  masonry  were  laid  in  one  month.  The  amount  of 
cement  per  cubic  yard  of  masonry  is  variously  stated  to  have 
been  0.6  to  0.75  bbl.  The  stone  was  granite. 

The  Spier  Falls  Dam  on  the  upper  Hudson  River  was  built 
of  rubble  concrete  containing  about  33  per  cent,  rubble  stone. 
The  concrete  was  a  1-2^-5  mixture,  and  the  engineer  states 
that  about  i  bbl.  of  cement  was  used  per  cubic  yard  of  rubble 
concrete.  This  high  percentage  of  cement  may  be  accounted 
for  by  the  fact  that  there  was  a  considerable  amount  of  rubble 
masonry  in  cement  mortar  included  in  the  total.  The  stones 
and  concrete  were  delivered  along  the  dam  by  cableways  and 
stiff-leg  derricks  set  on  the  downstream  sloping  face  of  the 
dam  delivered  them  from  the  cableways  into  place.  There 
were  two  laborers  to  each  mason  employed  in  placing  the 
materials,  wages  being  15  and  35  cts.  per  hour,  respectively. 
The  labor  cost  of  placing  the  materials  was  60  cts.  per  cubic 
yard  of  masonry.  The  stone  was  granite. 

Granite  rubble  laid  in  layers  on  beds  of  concrete  and  filled 
between  with  concrete  was  used  in  constructing  the  Hemet 
Dam  in  California.  The  concrete  was  a  1-3-6  mixture,  and 
was  thoroughly  tamped  under  and  between  the  stones.  For 
face  work  the  stones  were  roughly  scabbled  to  shape  and  laid 
in  mortar.  The  stone  was  taken  from  the  quarry  400  ft. 
away  and  delivered  directly  on  the  dam  by  cableways;  here 
two  derricks  handled  the  stone  into  place,  the  dam  being  only 
246  ft.  arc  length  on  top,  though  it  was  122^  ft.  high.  The 
cableways  would  take  a  lo-ton  load;  stones  could  be  taken 


104  CONCRETE    CONSTRUCTION. 

from  the  quarry,  hoisted  150  ft.  and  delivered  to  the  work  in 
40  to  60  seconds.  Common  labor  at  $1.75  per  day  was  used 
for  all  masonry  except  facing,  where  masons  at  $3.50  were  em- 
ployed. Cement  cost  delivered  $5  per  barrel,  of  which  from 
$i  to  $1.50  per  barrel  was  the  cost  of  hauling  23  miles  by  team 
over  roads  having  18  per  cent,  grades  in  places.  Sand  was 
taken  from  the  stream  bed  and  delivered  to  the  work  by  bucket 
conveyor.  "Under  favorable  conditions  some  of  the  masonry 
was  put  in  for  as  low  as  $4  per  cu.  yd."  There  were  31,100  cu. 
yds.  of  masonry  in  the  dam,  which  required  20,000  bbls.  of 
cement,  or  0.64  bbl.  per  cubic  yard. 

The  following  novel  method  of  making  rubble  concrete  was 
employed  in  enlarging  two  old  dams  and  in  constructing  two 
new  dams  for  a  small  water-works.  The  available  time  was 
short,  the  amount  of  work  was  too  small  and  too  scattered  to 
justify  the  installation  of  a  stone  crusher,  and  suitable  gravel 
was  not  at  hand.  Sufficient  small  boulders  in  old  walls,  and 
borrow  pits  and  on  surface  of  fields  were  available,  and  were 
used  with  thin  Portland  cement  mortar.  One  part  of  Alpha 
or  Lehigh  cement  and  three  parts  sand  were  mixed  dry  at  first 
and  then  wet  with  just  enough  water  to  make  the  resulting 
mortar  flow  by  gravity.  This  mortar  was  shoveled  into  the 
forms  continuously  by  one  set  of  men  while  other  men  were 
throwing  into  the  mortar  in  the  forms  the  boulders  which 
were  cleaned  and  broken  so  as  not  to  be  more  than  7  ins.  long. 
In  general  the  performance  was  continuous.  Three  mortar 
beds  were  placed  parallel  with,  and  against,  one  side  of  the 
forms,  with  spaces  of  about  4  ft.  between  the  ends  of  the  beds. 
The  boulders  were  dumped  on  the  opposite  side  of  the  forms. 
Two  men  shoveled  in  all  the  mortar  and  did  nothing  else. 
While  they  were  emptying  one  bed  the  mortar  was  being 
mixed  in  the  preceding  bed  by  two  other  men  and  the  ma- 
terials placed  in  the  third  bed  by  still  others.  Another  gang 
was  continually  throwing  in  the  boulders  and  small  stones 
and  still  another  was  breaking  stone.  One  man  should  keep 
the  mortar  well  stirred  while  the  bed  is  being  emptied.  About 
20  men  were  necessary  to  do  all  parts  of  the  work.  The  forms 
were  of  2-in.  planed  plank  tongued  and  grooved.  Especial 
pains  were  taken  to  make  the  forms  tight,  and  all  leaks  that 
appealed  were  quickly  stopped  with  dry  cement.  Some  pains 


RUBBLE   CONCRETE. 


105 


were  taken  to  prevent  a  flat  side  of  large  stones  from  coming 
in  direct  contact  with  the  forms,  but  round  boulders  and  small 
stones  needed  no  care  to  prevent  their  showing  in  the  finished 
work. 

In  conclusion  it  is  interesting  to  note,  perhaps,  the  earliest 
use  of  rubble  concrete  for  dam  construction  in  this  country  in 
constructing  the  Boyd's  Corner  Dam  on  the  Croton  River  near 
New  York.  This  dam  was  begun  in  1867  and  for  a  time  rubble 
concrete  was  used,  but  was  finally  discontinued,  due  to  the 
impression  that  it  might  not  be  water-tight.  The  specifica- 


Fig.   38.— Bridge  Abutment  of  Rubble  Concrete. 

tions  called  for  dry  concrete  to  be  thoroughly  rammed  in  be- 
tween the  rubble  stones,  and  to  give  room  for  this  ramming 
the  contractor  was  not  permitted  to  lay  any  two  stones  closer 
together  than  12  ins.  As  a  result  not  more  than  33  per  cent, 
of  the  concrete  was  rubble. 

Abutment  for  Railway  Bridge.— Figure  38  shows  a  bridge 
abutment  built  of  rubble  concrete  at  a  cost  of  about  $4.50  per 
cu.  yd.  The  concrete  was  a  1-2^-4^  mixture  laid  in  4-in. 
layers.  On  each  layer  were  laid  large  rubble  stones  bedded 


I06  CONCRETE    CONSTRUCTION. 

flat  -and  spaced  to  give  6-in.  vertical  joints ;  the  vertical  joints 
were  rilled  with  concrete  by  ramming  and  then  another  layer 
of  concrete  placed  and  so  son.  A  force  of  28  men  and  a  fore- 
man averaged  40  cu.  yds.  of  rubble  concrete  per  day.  The 
following  is  the  itemized  cost  per  cubic  yard,  not  including 
forms,  for  278  cu.  yds : 

Item.  Per  Cu.  Yd. 

0.82  bbls.  cement,  at  $2.60 $2.14 

0.22  cu.  yd.  sand,  at  $1.00 0.22 

0.52  cu.  yd.  broken  stone,  at  $0.94 0.49 

0.38  cu.  yd1,  rubble  stone,  at  $0.63 0.24 

Water   0.07 

Labor,  at  15  cts.  per  hour 1.19 

Foreman 0.09 


Total   '. $4.44 

Some  English  Data  on  Rubble  Concrete. — Railway  work, 
under  Mr.  John  Strain,  in  Scotland  and  Spain,  involved  the 
building  of  abutments,  piers  and  arches  of  rubble  concrete. 
The  concrete  was  made  of  i  part  cement  to  5  parts  of  ballast, 
the  ballast  consisting  of  broken  stone  or  slag  and  sand  mixed 
in.  proportions  determined  by  experiment.  The  materials  were 
mixed  by  turning  with  shovels  4  times  dry,  then  4  times  more 
during  the  addition  of  water  through  a  rose  nozzle.  A  bed  of 
concrete  6  ins.  thick  was  first  laid,  and  on  this  a  layer  of  rubble 
stones,  no  two  stones  being  nearer  together  than  3  ins.,  nor 
nearer  the  forms  than  3  ins.  The  stones  were  rammed  and 
probed  around  with  a  trowel  to  leave  no  spaces.  Over  each 
layer  of  rubble,  concrete  was  spread  to  a  depth  of  6  ins.  The 
forms  or  molds  for  piers  for  a  viaduct  were  simply  large  open 
boxes,  the  four  sides  of  which  could  be  taken  apart.  The  depth 
of  the  boxes  was  uniform,  and  they  were  numbered  from  the 
top  down,  so,  that,  knowing  the  height  of  a  given  pier,  the 
proper  box  for  the  base  could  be  selected.  As  each  box  was 
filled,  the  next  one  smaller  in  size  was  swung  into  place  with 
a  derrick.  The  following  bridge  piers  for  the  Tharsis  & 
Calanas  Railway  were  built: 


RUBBLE    CONCRETE. 


107 


Length  Height      No. 

Cu.  Yds. 

Weeks 

of           of           of 

in 

to 

Name. 

Bridge.  Piers.     Spans. 

Piers. 

Build. 

Ft.          Ft. 

Tamujoso  River. 

..   435          28          12 

1,737 

H/2 

Oraque  

4.23             31              II 

I  ^QO 

T  C 

T"      O                      O 

^-'Dy^ 

*«j 

Cascabelero        .  . 

480     30  to  80     10 

2,68O 

21 

No    1  6 

204.      28  to  ^O        7 

I  O4.6 

TfiU 

i/T1                        O              / 

x  J^/fcyv-' 

--/f 

Tiesa 

16;     i6to23       8 

4.2O 

A 

It  is  stated  that  the  construction  of  some  of  these  piers  in 
ordinary  masonry  would  have  taken  four  times  as  long.  The 
rock  available  for  rubble  did  not  yield  large  blocks,  conse- 
quently the  percentage  of  pure  concrete  in  the  piers  was  large, 
averaging  70  per  cent.  In  one  case,  where  the  stones  were 
smaller  than  usual,  the  percentage  of  concrete  was  76/2  per 
cent.  In  other  work  the  percentage  has  been  as  low  as  55 
per  cent.,  and  in  still  other  work  where  a  rubble  face  work  was 
used  the  percentage  of  concrete  has  been  40  per  cent. 

In  these  piers  the  average  quantities  of  materials  per  cubic 
yard  of  rubble  concrete  were : 

448  Ibs.  (0.178  cu.  yd.)  cement. 

0.36  cu.  yd.  sand. 

o. 68  cu.  yd.  broken  stone  (measured  loose  in  piles). 

0.30  cu.  yd.  rubble   (measured  solid). 

Several  railway  bridge  piers  and  abutments  in  Scotland  are 
cited.  In  one  of  these,  large  rubble  stones  of  irregular  size 
and  weighing  2  tons  each  were  set  inside  the  forms,  3  ins. 
away  from  the  plank  and  3  ins.  from  one  another.  The  gang 
to  each  derrick  was :  I  derrick  man  and  I  boy,  I  mason  and 
10  laborers,  and  about  one-quarter  of  the  time  of  I  carpenter 
and  his  helper  raising  the  forms.  For  bridges  of  400  cu.  yds., 
the  progress  was  12  to  15  cu.  yds.  a  day.  The  forms  were 
left  in  place  10  days. 

To  chip  off  a  few  inches  from  the  face  of  a  concrete  abut- 
ment that  was  too  far  out,  required  the  work  of  I  quarryman 
5  days  per  cu.  yd.  of  solid  concrete  chipped  off. 

Concrete  was  used  for  a  skew  arch  over  the  River  Dochart, 
on  the  Killin  Railway,  Scotland.  There  were  5  arches,  each 
of  30  ft.  span  on  the  square  or  42  ft.  on  the  skew,  the  skew 
being  45°.  The  piers  were  of  rubble  concrete.  The  concrete 


108  CONCRETE    CONSTRUCTION. 

in  the  arch  was  wheeled  300  ft.  on  a  trestle,  and  dumped  onto 
the  centers.  It  was  rammed  in  6-in.  layers,  which  were  laid 
corresponding  to  the  courses  of  arch  stones.  As  the  layers 
approached  the  crown  of  the  arch,  some  difficulty  was  experi- 
enced in  keeping  the  surfaces  perpendicular.  Each  arch  was 
completed  in  a  day. 

In  a  paper  by  John  W.  Steven,  in  Proc.  Inst.  C.  E.,  the  fol- 
lowing is  given : 

Rubble      Per  Cent. 

Concrete     Concrete     of  Rubble 

Per  Per          in  Rubble 

Cu.  Yd.       Cu.  Yd.       Concrete. 

Ardrossan   Harbor $6.00  $5«oo  20.0 

Irvine  Branch 7.00  3.68  63.6 

Calanas  &  Tharsis  Ry.  .  .     7.08  3.43  30.3 

Mr.  Martin  Murphy  describes  some  bridge  foundations  in 
Nova  Scotia.  Rubble  concrete  was  used  in  some  of  the  piers. 
The  rubble  concrete  consisted  of  I  part  cement,  2  parts  sand, 
i  part  clean  gravel,  and  5  parts  of  large  stones  weighing  20 
Ibs.  each  and  upwards.  The  sand,  cement  and  gravel  were 
turned  three  times  dry  and  three  times  wet,  and  put  into  the 
forms.  The  rubble  stones  were  bedded  in  the  concrete  by 
hand,  being  set  on  end,  2  or  3  ins.  apart.  No  rubble  stones 
were  placed  within  6  ins.  of  the  forms,  thus  leaving  a  face  of 
plain  concrete;  and  the  rubble  stones  were  not  carried  higher 
than  18  ins.  below  the  top  of  the  pier.  One  cubic  yard  of  this 
rubble  concrete  required  0.8  to  0.9  bbl.  of  cement. 

ASPHALT  CONCRETE.— Asphalt  or  tar  concrete  in 
which  steam  cinders  or  broken  stone  or  gravel  and  sand  are 
mixed  with  asphaltum  or  tar  instead  of  cement  paste  are  used 
to  some  extent  in  lining  reservoirs,  constructing  mill  floors, 
etc.  Such  mixtures  differ  in  degree  only  from  the  mixtures 
used  for  asphalt  street  paving,  for  discussion  of  which  the 
various  books  on  paving  and  asphalts  should  be  consulted. 
The  two  examples  of  asphalt  concrete  work  given  here  are 
fairly  representative  of  the  mixtures  and  methods  employed 
for  concrete  work  as  distinguished  from  asphalt  work. 

Slope  Paving  for  Earth  Dam. — Mr.  Robert  B.  Stanton  de- 
scribes a  small  log  dam  faced  upstream  with  earth,  upon  which 
was  laid  an  asphalt  concrete  lining  to  make  it  water  tight.  The 


RUBBLE   CONCRETE. 


109 


stone  was  broken  to  2-in.  pieces,  all  the  fines  being  left  in  and 
sufficient  fine  material  added  to  fill  the  voids.  The  stone  was 
heated  and  mixed  in  pans  or  kettles  from  a  street  paving  out- 
fit; and  the  asphaltum  paste,  composed  of  4  parts  California 
refined  asphaltum  and  I  part  crude  petroleum,  was  boiled  in 
another  kettle.  The  boiling  hot  paste  was  poured  with  ladles 
over  the  hot  stone,  and  the  whole  mixed  over  the  fire  with 
shovels  and  hoes.  The  asphalt  concrete  was  taken  away  in 
hot  iron  wheelbarrows,  placid  in  a  4-in.  layer  rammed  and 
ironed  with  hot  irons.  The  concrete  was  laid  in  strips  4  to  6 
ft.  wide,  the  edges  being  coated  with  hot  paste.  After  the 
whole  reservoir  was  lined,  it  was  painted  with  the  asphalt 
paste,  boiled  much  longer,  until  when  cold  it  was  hard  and 
brittle,  breaking  like  glass  under  the  hammer.  This  paste  was 
put  on  very  hot  and  ironed  down.  It  should  not  be  more 
than  ^s -in.  thick  or  it  will  ''creep"  on  slopes  of  \y2  to  i.  After 
two  hot  summers  and  one  cold  winter  there  was  not  a  single 
crack  anywhere  in  the  lining.  A  mixture  of  sand  and  asphalt 
will  creep  on  slopes  of  il/2  to  i,  but  asphalt  concrete  will  not. 
With  asphalt  at  $20  a  ton,  and  labor  at  $2  a  day,  the  cost  was 
15  cts.  a  sq.  ft.  for  4-in.  asphalt  concrete.  On  a  high  slope  Mr. 
Stanton  recommends  making  slight  berms  every  6  ft.  to  sup- 
port the  concrete  and  prevent  creeping.  Asphalt  concrete  re- 
sists the  wear  of  wind  and  water  that  cuts  away  granite  and 
iron. 

Base  for  Mill  Floor. — In  constructing  17,784  sq.  ft.  of  tar 
concrete  base  for  a  mill  floor,  Mr.  C.  H.  Chadsey  used  a  sand, 
broken  stone  and  tar  mixture  mixed  in  a  mechanical  mixer. 
The  apparatus  used  and  the  mode  of  procedure  followed  were 
as  follows : 

Two  parallel  8-in.  brick  walls  26  ft.  long  were  built  4  ft. 
apart  and  2l/2  ft.  high  to  form  a  furnace.  On  these  walls  at 
one  end  was  set  a  4x6x2  ft.  steel  plate  tar  heating  tank.  Next 
to  this  tank  for  a  space  of  4x8  ft.  the  walls  were  spanned  be- 
tween with  steel  plates.  This  area  was  used  for  heating  sand. 
Another  space  of  4x8  ft.  was  covered  with  il/>  in.  steel  rods 
arranged  to  form  a  grid ;  this  space  was  used  for  heating  the 
broken  stones.  The  grid  proved  especially  efficient,  as  it  per- 
mitted the  hot  air  to  pass  up  through  the  stones,  while  a  small 
cleaning  door  at  the  ground  allowed  the  screenings  which 


HO  CONCRETE    CONSTRUCTION. 

dropped  through  the  grid  to  be  raked  out  and  added  to  the 
mixture.  A  fire  from  barrel  staves  and  refuse  wood  built 
under  the  tank  end  was  sufficient  to  heat  the  tar,  sand  and 
stone. 

For  mixing  the  materials  a  Ransome  mixer  was  selected 
for  the  reason  that  heat  could  be  supplied  to  the  exterior  of 
the  drum  by  building  a  wood  fire  underneath.  This  fire  was 
maintained  to  prevent  the  mixture  from  adhering  to  the  mix- 
ing blades,  and  it  proved  quite  effective,  though  occasionally 
they  would  have  to  be  cleaned  with  a  chisel  bar,  particularly 
when  the  aggregate  was  not  sufficiently  heated  before  being 
admitted  to  the  mixer.  A  little  "dead  oil"  applied  to  the 
discharge  chute  and  to  the  shovels,  wheelbarrows  and  other 
tools  effectually  prevented  the  concrete  from  adhering  to 
them. 

The  method  of  depositing  the  concrete  was  practically  the 
same  as  that  used  in  laying  cement  sidewalks.  Wood  strips 
attached  to  stakes  driven  into  the  ground  provided  templates 
for  gaging  the  thickness  of  the  base  and  for  leveling  off  the 
surface.  The  wood  covering  consisted  of  a  layer  of  2-in. 
planks,  covered  by  matched  hardwood  flooring.  In  placing 
the  planking,  the  base  was  covered  with  a  ^4-in.  layer  of  hot 
pitch,  into  which  the  planks  were  pressed  immediately,  the  last 
plank  laid  being  toe-nailed  to  the  preceding  plank  just  enough 
to  keep  the  joint  tight.  After  a  few  minutes  the  planks  ad- 
hered so  firmly  to  the  base  that  they  could  be  removed  only 
with  difficulty.  The  hardwood  surface  was  put  on  in  the  usual 
manner.  The  prices  of  materials  and  wages  for  the  work  were 
as  follows : 

Pitch,  bulk,  per  Ib .  .$  0.0075 

Gravel,  per  cu.  yd 1.50 

Spruce  sub-floor,  per  M.  ft.  B.  M 15.00 

Hardwood  surface,  per  M.  ft.  B.  M 33.00 

Laborers,  per  lo-hour  day 1.50 

Foreman,  per  lo-hour  day 4.00 

Carpenters,  per  lo-hour  day 2.00 

At  these  prices  and  not  including  a  small  administration 
cost  or  the  cost  of  tools  and  plant,  the  cost  of  the  floor  con- 
sisting of  4^2  ins.  of  concrete,  2  ins.  of  spruce  sub-flooring  and 
J^-in.  hardwood  finish  was  as  follows  per  square  foot: 


RUBBLE   CONCRETE.  Ill 

Pitch   .......................  -  ...........  •  ......      -  $o-°4 

Gravel  ..  .....  .  ......  ......  -  -  -  -  •  •  <  «  •  •  •  •  •  •  •  •  •  ........  °-°2 

Spruce,  for  sub-floor.  ............  .....  .  ........  .  .  .  <  •  0.03 

Hardwood  for  surfacing.  .  .  .  .  ----  .*,;..•...,...  ----  •  •  •  °-°35 

Labor,  mixing    ............  ,...........••»••»••»••••   0.03 

Labor,  laying  ......  .  .  ...»  .  ........  •  -  •  •  •  •  •  -  °  «  •  •  •  -  •  •  •  °-OI5 

Carpenter  work   ......  .  .  .  .  .  .  .  .  .  .  .  .  .  .  -  ......  «  •  •  •  •  •  •  • 


Total  per  square  foot 


CHAPTER  VII. 

METHODS   AND   COST   OF   LAYING  CONCRETE   IN 
FREEZING  WEATHER. 

Reinforced  concrete  work  may  be  done  in  freezing  weather 
if  the  end  to  be  gained  warrants  the  extra  cost.  Laboratory 
experiments  show  beyond  much  doubt  that  Portland  cement 
concrete  which  does  not  undergo  freezing  temperatures  until 
final  set  has  taken  place,  or  which,  if  frozen  before  it  has  set, 
is  allowed  to  complete  the  setting  process  after  thawing  with- 
out a  second  interruption  by  freezing,  does  not  suffer  loss  of 
ultimate  strength  or  durability.  These  requirements  for  safety 
may  be  satisfied  by  so  treating  the  materials  or  compounding 
the  mixture  that  freezing  will  not  occur  at  normal  freezing 
temperature  or  else  will  be  delayed  until  the  concrete  has  set, 
by  so  housing  in  the  work  and  artificially  treating  the  in- 
closed space  that  its  temperature  never  falls  as  low  as  the 
freezing  point,  or,  by  letting  the  concrete  freeze  if  it  will  and 
then  by  suitable  protection  and  by  artificial  heating  produce 
and  maintain  a  thawing  temperature  until  set  has  taken  place. 

LOWERING  THE  FREEZING  POINT  OF  THE  MIX- 
ING'WATER. — Lowering  the  freeezing  point  of  the  mixing 
water  is  the  simplest  and  cheapest  method  by  which  concrete 
can  be  mixed  and  deposited  in  freezing  weather.  The  method 
consists  simply  in  adding  some  substance  to  the  water  which 
will  produce  a  brine  or  emulsion  that  freezes  at  some  tem- 
perature below  32°  F.  determined  by  the  substance  added  and 
the  richness  of  the  admixture.  A  great  variety  of  substances 
may  be  added  to  water  to  produce  low  freezing  brines,  but  in 
concrete  work  only  those  may  be  used  that  do  little  or  no  in- 
jury to  the  strength  and  durability  of  the  concrete.  Practice 
has  definitely  determined  only  one  of  these,  namely,  sodium 
chloride  or  common  salt,  though  some  others  have  been  used 
successfully  in  isolated  cases.  A  point  to  be  borne  in  mind  is 
that  cold  retards  the  setting  of  cement  and  that  the  use  of 

112 


CONCRETING   IN   FREEZING    WEATHER. 


anti-freezing  mixtures  emphasizes  this  phenomenon  and  its 
attendant  disadvantages  in  practical  construction.  The  ac- 
companying diagram,  Fig.  39,  based  on  the  experiments  of 
Tetmajer,  show  the  effect  on  the  freezing  point  of  water  by 
the  admixtures  of  various  substances  that  have  been  sug- 
gested for  reducing  the  freezing  point  of  mortar  and  concrete 
mixtures. 

Common  Salt  (Sodium  Chloride). — The  substance  most 
usually  employed  to  lower  the  freezing  point  of  water  used  in 
concrete  is  common  salt.  Laboratory  experiments  show  that 
the  addition  of  salt  retards  the  setting  and  probably  lowers 
the  strength  of  cement  at  short  periods,  but  does  not,  when 
not  used  to  excess,  injure  the  ultimate  strength.  The  amount 
beyond  which  the  addition  of  salt  begins  to  affect  injuriously 


10 


20          30         40          50 
Per  Gen*  o-f  Solution. 


60 


70 


80 


Fig.   39.— Diagram   Showing  Effect  on  Freezing  Point  of  Water  by  Admix- 
ture of  Various  Substances. 

the  strength  of  cement  is  stated  variously  by  various  author- 
ities. Sutcliffe  states  that  it  is  not  safe  to  go  beyond  7  or  8 
per  cent,  by  weight  of  the  water ;  Sabin  places  the  safe  figures 
at  10  per  cent.,  and  the  same  figure  is  given  by  a  number  of 
other  American  experimenters.  A  number  of  rules  have  been 
formulated  for  varying  the  percentage  of  salt  with  the  tem- 
perature of  the  atmosphere.  Prof.  Tetmajer's  rule  as  stated 
by  Prof.  J.  B.  Johnson,  is  to  add  I  per  cent,  of  salt  by  weight 
of  the  water  for  each  degree  Fahrenheit  below  32°.  A  rule 
quoted  by  many  writers  is  "i  Ib.  of  salt  to  18  gallons  of  water 
for  a  temperature  of  32°  F.,  and  an  increase  of  I  oz.  for  each 
degree  lower  temperature."  This  rule  gives  entirely  inade- 
quate amounts  to  be  effective,  the  percentage  by  weight  of  the 
water  being  about  I  per  cent.  The  familiar  rules  of  enough 


114 


CONCRETE    CONSTRUCTION. 


salt  to  make  a  brine  that  will  "float  an  egg"  or  "float  a  potato" 
are  likewise  -untrustworthy ;  they  call  respectively,  according 
to  actual  tests  made  by  Mr.  Sanford  E.  Thompson,  for  15  per 
cent,  and  n  per  cent,  of  salt  which  is  too  much,  according  to 
the  authorities  quoted  above,  to  be  used  safely.  In  practice 
an  arbitrary  quantity  of  salt  per  barrel  of  cement  or  per  100 
Ibs.  of  water  is  usually  chosen.  Preferably  the  amount  should 
be  stated  in  terms  of  its  percentage  by  weight  of  the  water, 
since  if  stated  in  terms  of  pounds  per  barrel  of  cement  the 
richness  of  the  brine  will  vary  with  the  richness  of  the  con- 
crete mixture,  its  composition,  etc.  As  examples  of  the  per- 
centages used  in  practice,  the  following  works  may  be  quoted : 
New  York  Rapid  Transit  Railway,  9  per  cent,  by  weight  of 
the  water ;  Foster-Armstrong  Piano  Works,  6  per  cent,  by 
weight  of  the  water.  In  summary,  it  would  seem  that  if  a 
rule  for  the  use  of  salt  is  to  be  adopted  that  of  Tetmajer,  which 
is  to  add  i  per  cent,  by  weight  of  the  water  for  each  degree 
Fahrenheit  below  32°,  is  as  logical  and  accurate  as  any.  It 
should,  however,  be  accompanied  by  the  proviso  that  no  more 
than  10  per  cent,  by  weight  of  salt  should  be  considered  safe 
practice,  and  that  if  the  frost  is  too  keen  for  this  to  avail  some 
other  method  should  be  adopted  or  the  work  stopped.  It  may 
be  taken  that  each  unit  per  cent,  of  salt  added  to  water  re- 
duces the  freezing  temperature  of  the  brine  about  1.08°  F. ;  a 
10  per  cent,  salt  brine  will  therefore  freeze  at  32°  —  11°  =21° 
F.  The  range  of  efficiency  of  salt  as  a  preventative  of  frost  in 
mixing  and  laying  concrete  is,  obviously,  quite  limited. 

HEATING  CONCRETE  MATERIALS.— Heating  the 
sand,  stone  and  mixing  water  acts  both  to  hasten  the  setting 
and  to  lengthen  the  time  before  the  mixture  becomes  cold 
enough  to  freeze.  At  temperatures  not  greatly  below  freezing 
the  combined  effects  are  sufficient  to  ensure  the  setting  of  the 
concrete  before  it  can  freeze.  More  specific  data  of  efficiency 
are  difficult  to  arrive  at.  There  are  no  test  data  that  show 
howlong  it  takes  a  concrete  mixture  at  a  certain  temperature 
to  lose  its  heat  and  become  cold  enough  to  freeze  at  any  spe- 
cific temperature  of  the  surrounding  air,  and  a  theoretical  cal- 
culation of  this  period  is  so  beset  with  difficulties  as  to  be  im- 
practicable. Strength  tests  of  concrete  made  with  heated 
materials  have  shown  clearly  enough  that  the  he^,t;  -  y  has  no 


CONCRETING   IN   FREEZING    WEATHER. 


effect  worth  mentioning  on  either  strength  or  durability. 
Either  the  water,  the  sand,  the  aggregate  or  all  three  may  be 
heated;  usually  the  cement  is  not  heated  but  it  may  be  if  de- 
sired. 

Portable  Heaters. — An  ordinary  half  cylinder  of  sheet  steel 
set  on  the  ground  like  an  arch  is  the  simplest  form  of  sand 
heater.  A  wood  fire  is  built  under  the  arch  and  the  sand  to 
be  heated  is  heaped  on  the  top  and  sides.  The  efficiency  of 
this  device  may  be  improved  by  closing  one  end  of  the  arch 
and  adding  a  short  chimney  stack,  but  even  the  very  crude 
arrangement  of  sheets  of  corrugated  iron  bent  to  an  arc  will 
do  good  service  where  the  quantities  handled  are  small.  This 
form  of  heater  may  be  used  for  stone  or  gravel  in  the  same 
manner  as  for  sand.  It  is  inexpensive,  simple  to  operate  and 
requires  only  waste  wood  for  fuel,  but  unless  it  is  fired  with 

in 


,± 


k efc*. >i 

Fire       End. 


Side          Elevation. 

Fig.   40. — Portable   Sand,    Stone  and  Water  Heater. 

exceeding  care  the  sand  in  contact  with  the  metal  will  be 
burned.  The  drawings  of  Fig.  40  show  the  construction  of  a 
portable  heater  for  sand,  stone  and  water  used  in  constructing 
concrete  culverts  on  the  New  York  Central  &  Hudson  River 
Railroad.  This  device  weighs  1,200  Ibs.,  and  costs  about  $50. 
Heating  in  Stationary  Bins. — The  following  arrangement 
for  heating  sand  and  gravel  in  large  quantities  in  bins  was  em- 
ployed in  constructing  the  Foster-Armstrong  Piano  Works  at 
Rochester,  N.  Y.  The  daily  consumption  of  sand  and  gravel 
on  this  work  was  about  50  cu.  yds.  and  100  cu.  yds.,  re- 
spectively. To  provide  storage  for  the  sand  and  gravel,  a  bin 
16  ft.  square  in  projected  plan  was  constructed  with  vertical 
sides  and  a  sloping  bottom  as  illustrated  in  Fig.  41.  This  bin 
was  divided  by  a  vertical  partition  into  a  large  compartment 


Il6  CONCRETE    CONSTRUCTION. 

for  gravel  and  a  small  compartment  for  sand  and  was  provided 
with  two  grates  of  boiler  tubes  arranged  as  shown.  These 
grates  caused  V-shaped  cavities  to  be  formed  beneath  in  the 
gravel  and  sand.  Into  these  cavities  penetrated  through  one 
end  of  the  bin  6-in.  pipes  from  a  hot  air  furnace  and  i-in.  pipes 
from  a  steam  boiler.  The  hot  air  pipes  merely  pass  through 
the  wall  but  the  steam  pipes  continue  nearly  to  the  opposite 
side  of  the  bin  and  are  provided  with  open  crosses  at  intervals 
along  their  length.  In  addition  to  the  conduits  described 
there  is  a  small  pipe  for  steam  located  below  and  near  the  bot- 
tom of  the  bin.  The  hot  air  pipes  connected  with  a  small  fur- 
nace and  air  was  forced  through  them  by  a  Sturtevant  No.  6 
blower.  The  steam  pipes  connected  with  the  boiler  of  a  steam 
heating  system  installed  to  keep  the  buildings  warm  during 
construction. 


Fig.   41. — Bin   Arrangement    for  Heating   Sand  and    Stone. 

Other  Examples  of  Heating  Materials. — In  the  construction 
of  the  power  plant  of  trie  Billings  (Mont.)  Water  Power  Co., 
practically  all  of  the  concrete  work  above  the  main  floor  level 
was  put  in  during  weather  so  cold  that  it  was  necessary  to 
heat  both  the  gravel  and  water  used.  A  sand  heater  was  con- 
structed of  four  I5~ft.  lengths  of  15-in.  cast  iron  pipe,  two 
in  series  and  the  two  sets  placed  side  by  side.  This  gave  a 
total  length  of  30  ft.  for  heating,  making  it  possible  to  use  the 
gravel  from  alternate  ends  and  rendering  the  heating  process 
continuous.  The  gravel  was  dumped  directly  on  the  heater, 
thus  avoiding  the  additional  expense  of  handling  it  a  second 
time.  The  heater  pipes  were  laid  somewhat  slanting,  the  fire 
being  built  in  the  lower  end.  A  lo-ft.  flue  furnished  sufficient 


CONCRETING   IN   FREEZING    WEATHER. 


117 


draft  for  all  occasions.  With  this  arrangement  it  was  pos- 
sible to  heat  the  gravel  to  a  temperature  of  80°  or  90°  F.  even 
during  the  coldest  weather.  Steam  for  heating  the  water  was 
available  from  the  plant.  The  temperature  at  which  the  con- 
crete was  placed  in  the  forms  was  kept  between  65°  and  75°  F. 
This  was  regulated  by  the  man  on  the  mixer  platform  by  vary- 
ing the  temperature  of  the  water  to  suit  the  conditions  of  the 
gravel.  When  the  ingredients  were  heated  in  this  manner  it 
was  found  advisable  to  mix  the  concrete  "sloppy,"  using  even 
more  water  than  would  be  commonly  used  in  the  so-called 
"sloppy"  concrete.  No  difficulty  was  experienced  with  tem- 
perature cracks  if  the  concrete,  when  placed,  was  not  above 
75°  F.  All  cracks  of  this  nature  which  did  appear  were  of 
no  consequence,  as  they  never  extended  more  than  l/2  in. 
below  the  surface.  The  concrete  was  placed  in  as  large  masses 
as  possible.  It  was  covered  nights  with  sacks  and  canvas  and, 
when  the  walls  were  less  than  3  ft.  in  width,  the  outside  of 
the  forms  was  lagged  with  tar  paper.  An  air  space  was 
always  left  between  the  surface  of  the  concrete  and  the  cov- 
ering. Under  these  conditions  there  \vas  sufficient  heat  in  the 
mass  to  prevent  its  freezing  for  several  days,  which  was  ample 
time  for  permanent  setting. 

During  the  construction  in  1902  of  the  Wachusett  Dam  at 
Clinton,  Mass.,  for  the  Metropolitan  Water  Works  Commis- 
sion the  following  procedures  were  followed  in  laying  con- 
crete in  freezing  weather:  After  November  15  all  masonry 
was  laid  in  Portland  cement,  and  after  November  28  the  sand 
and  water  were  heated  and  salt  added  in  the  proportion  of 
4  Ibs.  per  barrel  of  cement.  The  sand  was  heated  in  a  bin, 
ibl/2  x  i$y2  x  10  ft.  deep,  provided  with  about  20  coils  of  2-in. 
pipe,  passing  around  the  inside  of  the  bin.  The  sand,  which 
was  dumped  in  the  top  of  the  bin  and  drawn  from  the  bottom, 
remained  there  long  enough  to  become  warm.  The  salt  for 
each  batch  of  mortar  was  dissolved  in  the  water  which  was 
heated  by  steam ;  steam  was  also  used  to  thaw  ice  from  the 
stone  masonry.  The  laying  of  masonry  was  not  started  on 
mornings  when  the  temperature  was  lower  than  18°  F.  above 
zero,  and  not  even  with  thisj:emperature  unless  the  day  was 
clear  and  higher  temperature  expected.  At  the  close  of  each 
day  the  masonry  built  was  covered  with  canvas. 


ng  CONCRETE    CONSTRUCTION. 

In  the  construction  of  dams  for  Huronian  Company's  power 
development  in  Canada  a  large  part  of  the  concrete  work  in 
dams,  and  also  in  power  house  foundations,  was  done  in  win- 
ter, with  the  temperature  varying  from  a  few  degrees  of  frost 
to  15  degrees  below  zero,  and  on  several  occasions  much 
lower.  No  difficulty  was  found  in  securing  good  concrete 
work,  the  only  precaution  taken  being  to  heat  the  mixing 
water  by  turning  a  fy-'m.  steam  pipe  into  the  water  barrel  sup- 
plying the  mixer,  and,  during  the  process  of  mixing,  to  use  a 
jet  of  live  steam  in  the  mixer,  keeping  the  cylinder  closed  by 
wooden  coverings  during  the  process  of  mixing.  No  attempt 
was  made  to  heat  sand  or  stone.  In  all  the  winter  work  care 
was  taken  to  use  only  cement  which  would  attain  its  initial  set 
in  not  more  than  65  minutes. 

In  constructing  a  concrete  arch  bridge  at  Piano,  111.,  the 
sand  and  gravel  were  heated  previous  to  mixing  and  the 
mixed  concrete  after  placing  was  kept  from  freezing  by  playing 
a  steam  jet  from  a  hose  connected  with  the  boiler  of  the  mixer 
on  the  surface  of  the  concrete  until  it  was  certain  that  initial 
set  had  taken  place.  Readings  taken  with  thermometers 
showed  that  in  no  instance  did  the  temperature  of  the  con- 
crete fall  below  32°  F.  within  a  period  of  10  or  12  hours  after 
placing. 

From  experience  gained  in  doing  miscellaneous  railway 
work  in  cold  weather  Mr.  L.  J.  Hotchkiss  gives  the  following: 

"For  thin  reinforced  walls,  it  is  not  safe  to  rely  on  heating 
the  water  alone  or  even  the  water  and  sand,  but  the  stone  also 
must  be  heated  and  the  concrete  when  it  goes  into  the  forms 
should  be  steaming  hot.  For  mass  walls  the  stone  need  not  be 
heated  except  in  very  cold  weather.  Where  concrete  is  mixed 
in  small  quantities  the  water  can  be  heated  by  a  wood  fire, 
and  if  a  wood  fire  be  kept  burning  over  night  on  top  of  the 
piles  of  stone  and  sand  a  considerable  quantity  can  be  heated. 
The  fire  can  be  kept  going  during  the  day  and  moved  back  on 
the  pile  as  the  heated  material  is  used.  This  plan  requires  a 
quantity  of  fuel  which  in  most  cases  is  prohibitive  and  is  not 
sufficient  to  supply  a  power  mixer.  For  general  use  steam  is 
far  better. 

"A  convenient  method  is  to  build  a  long  wooden  box  8  or 
10  in.  square  with  numerous  holes  bored  in  its  sides.  This  is 


CONCRETING   IN   FREEZING    WEATHER.  119 

laid  on  the  ground,  connected  with  a  steam  pipe  and  covered 
with  sand,  stone  or  gravel.  The  steam  escaping  through  the 
holes  in  the  box  will  heat  over  night  a  pile  of  sand,  or  sand 
and  gravel,  8  or  10  ft.  high.  Perforated  pipes  can  be  substi- 
tuted for  boxes.  Material  can  be  heated  more  rapidly  if  the 
steam  be  allowed  to  escape  in  the  pile  than  if  it  is  confined  in 
pipes  which  are  not  perforated.  Crushed  stone  requires  much 
more  heat  than  sand  or  sand  and  gravel  mixed  because  of 
the  greater  volume  of  air  spaces.  In  many  cases  material 
which  has  already  been  unloaded  must  be  heated.  The  ex- 
pense of  putting  steam  boxes  or  pipes  under  it  is  considerable. 
To  avoid  this  one  or  more  steam  jets  may  be  used,  the  end  of 
the  jet  pipe  being  pushed  several  feet  into  the  pile  of  material. 
If  the  jets  are  connected  up  with  steam  hose  they  are  easily 
moved  from  place  to  place.  It  is  dimcult  to  heat  stone  in  this 
way  except  in  moderate  weather. 

"On  mass  work  and  at  such  temperatures  as  are  met  with 
in  this  latitude  (Chicago,  111.)  it  is  not  usually  necessary  to 
protect  concrete  which  has  been  placed  hot  except  in  the  top 
of  the  form.  This  can  be  done  by  covering  the  top  of  the 
form  with  canvas  and  running  a  jet  of  steam  under  it.  If 
canvas  is  not  available  boards  and  straw  or  manure  answer 
the  purpose.  If  heat  is  kept  on  for  36  hours  after  completion, 
this  is  sufficient,  except  in  unusually  cold  weather.  The  above 
treatment  is  all  that  is  required  for  reinforced  retaining  walls 
of  ordinary  height.  But  where  box  culverts  or  arches  carrying 
heavy  loads  must  be  placed  in  service  as  soon  as  possible,  the 
only  safe  way  is  to  keep  the  main  part  of  the  structure  warm 
until  the  concrete  is  thoroughly  hardened.  Forms  for  these 
structures  can  be  closed  at  the  ends  and  stoves  or  salamanders 
kept  going  inside,  or  steam  heat  may  be  used.  The  outside 
may  be  covered  with  canvas  or  boards,  and  straw  and  steam 
jets  run  underneath.  After  the  concrete  has  set  enough  to 
permit  the  removal  of  the  outer  forms  of  box  culverts,  fires 
may  be  built  near  the  side  walls  and  the  concrete  seasoned 
rapidly.  Where  structures  need  not  be  loaded  until  after  the 
arrival  of  warm  weather,  heat  may  be  applied  for  36  hours, 
and  the  centering  left  in  place  until  the  concrete  has  hardened. 
Careful  inspection  of  winter  concrete  should  be  made  before 
loads  are  applied.  In  this  connection  it  may  be  noted  that 


120  CONCRETE    CONSTRUCTION. 

concrete  which  has  been  partly  seasoned  and  then  frozen, 
closely  resembles  thoroughly  seasoned  concrete.  Pieces 
broken  off  with  a  smooth  fracture  through  all  the  stones  and 
showing  no  frost  marks,  when  thawed  out,  can  be  broken 
with  the  hands/' 

In  building  Portland  cement  concrete  foundations  for  the 
West  End  St.  Ry.,  Boston,  and  the  Brooklyn  Heights  R.  R., 
much  of  the  work  was  done  in  winter.  A  large  water-tight 
tank  was  constructed,  of  such  size  that  three  skips  or  boxes 
of  stone  could  be  lowered  into  it.  The  tank  was  rilled  with 
water,  and  a  jet  of  steam  kept  the  water  hot  in  the  coldest 
weather.  The  broken  stone  was  heated  through  to  the  tem- 
perature of  the  water  in  a  few  minutes.  One  of  the  stone 
boxes  was  then  hoisted  out,  and  dumped  on  one  side  of  the 
mixing  machine,  and  then  run  through  the  machine  with  sand, 
cement  and  water.  The  concrete  was  wheeled  to  place  with- 
out delay  and  rammed  in  12-in.  layers.  The  heat  was  retained 
until  the  cement  was  set.  In  severely  cold  weather  the  sand 
was  heated  and  the  mixing  water  also.  A  covering  of  hay  or 
gunnysacks  may  be  used. 

COVERING  AND  HOUSING  THE  WORK.— Methods 
of  covering  concrete  to  protect  it  from  light  frosts  such  as 
may  occur  over  night  will  suggest  themselves  to  all ;  sacking, 
shavings,  straw,  etc.,  may  all  be  used.  Covering  wall  forms 
with  tar  paper  nailed  to  the  studding  so  as  to  form  with  the 
lagging  a  cellular  covering  is  an  excellent  device  and  will 
serve  in  very  cold  weather  if  the  sand  and  stone  have  been 
heated.  From  these  simple  precautions  the  methods  used  may 
range  to  the  elaborate  systems  of  housing  described  in  the  fol- 
lowing paragraphs. 

Method  of  Housing  in  Dam,  Chaudiere  Falls,  Quebec. — In 
constructing  a  dam  for  the  water  power  plant  at  Chaudiere 
Falls,  P.  Q.,  the  work  was  housed  in.  The  wing  dam  and  its 
end  piers  aggregated  about  250  ft.  in  length  by  about  20  ft.  in 
width.  A  house  100  ft.  long  and  24  ft.  wide  was  constructed 
in  sections  about  10  ft.  square  connected  by  cleats  with  bolts 
and  nuts.  This  house  was  put  up  over  the  wing  dam.  It  was 
20  ft.  high  to  the  eaves,  with  a  pitched  roof,  and  the  ends  were 
closed  up ;  in  the  roof  on  the  forebay  side  were  hatchways 
with  sliding  doors  along  the  whole  length.  Small  entrance 


CONCRETING   IN   FREEZING   WEATHER.  121 

doors  for  the  workmen  were  provided  in  the  ends  of  the 
building.  The  house  was  heated  by  a  number  of  cylindrical 
sheet-iron  stoves  about  18  ins.  in  diameter  by  24  ins.  high, 
burning  coke ;  thermometers  placed  at  different  points  in  the 
shed  gave  warning  to  stop  work  when  the  temperature  fell 
below  freezing,  which,  however,  rarely  occurred.  Mixing 
boards  were  located  in  the  shed,  and  concrete,  sand  and 
broken  stone  were  supplied  in  skipfuls  by  guy  derricks  located 
in  the  forebay,  which  passed  the  material  through  the  hatch- 
ways in  the  roof,  the  proper  hatchway  being  opened  for  the 
purpose  and  quickly  closed.  The  mortar  was  first  mixed  on 
a  board,  and  then  a  skip-load  of  stone  was  dumped  into  the 
middle  of  the  batch  and  the  whole  well  mixed.  The  water  was 
made  lukewarm  by  introducing  a  steam-jet  into  several  casks 
which  were  kept  full.  The  sand  was  heated  outside  in  the  fore- 
bay  on  an  ordinary  sand  heater.  The  broken  stone  was  heated 
in  piles  by  a  steam-jet;  a  pipe  line  on  the  ground  was  made  up 
of  short  lengths  of  straight  pipe  alternating  with  T-sections — 
turned  up.  The  stone  was  piled  3  to  4  ft.  deep  over  the  pipe 
and  a  little  steam  turned  into  the  pipe.  Several  such  piles 
kept  going  all  the  time  supplied  enough  stone  for  the  work; 
the  stone  was  never  overheated,  and  was  moist  enough  not  to 
dry  out  the  mortar  when  mixed  with  it.  In  this  manner  the 
concreting  was  successfully  carried  on  and  the  wing  dam  built 
high  enough  to  keep  high  water  out  of  the  forebay. 

Some  danger  from  freezing  was  also  encountered  the  next 
season,  when  the  last  part  of  the  wing  dam  was  being  con- 
structed. This  work  was  done  when  the  temperature  was 
close  to  freezing,  and  it  became  necessary  to  keep  the  freshly 
placed  concrete  warm  over  night.  This  was  done  by  covering 
the  work  loosely  with  canvas,  under  which  the  nozzle  of 
a  steam  hose  was  introduced.  By  keeping  a  little  steam  going 
all  night  the  concrete  was  easily  kept  above  freezing  tem- 
perature. 

Method  of  Housing  in  Building  Work. — The  following 
method  of  housing  in  building  work  is  used  by  Mr.  E.  L. 
Ransome.  The  feature  of  the  system  is  that  the  enclosing 
structure  is  made  up  of  a  combination  of  portable  units  which 
can  be  used  over  and  over  again  in  different  jobs.  The  con- 
struction is  best  explained  in  connection  with  sketches. 


122 


CONCRETE    CONSTRUCTION. 


Figure  43  shows  a  first  floor  wall  column  with  the  wall  girder 
surmounting  it  and  the  connecting  floor  system.  It  will  be 
seen  that  the  open  sides  are  enclosed  by  canvas  curtains  and 
the  floor  slab  is  covered  with  wood  shutters.  The  curtains 
are  composed  of  separate  pieces  so  devised  that  they  may  be 
attached  to  each  other  by  means  of  snaps  and  eyes ;  one  of 
these  curtain  units  is  shown  by  Fig.  42.  Referring  now  to 
Fig.  43,  the  curtain  A  is  held  by  the  tying-rings  to  a  con- 


Rear. 


Fig.   42.  -^Canvas  Curtain  for 
Enclosing  Open  Walls. 


Fig    43.— Sketch   Showing  Method  of 
Applying  Curtains   to  Open  Walls. 


tinuous  string  piece  B,  the  upper  portion  or  flap  D  being  held 
down  by  a  metal  bar  or  other  heavy  object  so  as  to  lap  over 
the  floor  covers  E.  The  lower  edge  of  the  curtain  is  attached  to 
the  string  piece  C.  The  sketch  has  been  made  to  show  how 
the  curtain  adjusts  itself  to  irregular  projections  such  as  the 
supports  for  a  wall  girder  form ;  to  prevent  the  curtain  tear- 
ing on  such  projections  it  is  well  to  cover  or  wrap  the  rough 
edges  with  burlap,  bagging  or  other  convenient  material.  The 
details  of  the  wooden  floor  covers  are  shown  by  Fig.  44 ;  they 
are  constructed  so  as  to  give  a  hollow  space  between  them 


CONCRETING  IN   FREEZING   WEATHER. 


123 


and  the  floor  and  holes  are  left  in  the  floor  slab  as  at  H, 
Fig.  43,  to  permit  the  warm  air  from  below  to  enter  this  hol- 
low space.  This  warm  air  is  provided  by  heating  the  enclosed 
story  of  the  building  by  any  convenient  adequate  means.  In 
constructing  factory  buildings,  50  x  200  ft.  in  plan  at 
Rochester,  N.  Y.,  Mr.  Ransome  used  a  line  of  ^4  to  %-in. 
steam  pipe  located  at  floor  level  and  running  around  all  four 
sides  and  a  similar  line  running  lengthwise  of  the  building  at 


ENG. 
NEWS. 


,_- 


--4 


t- 


—  JL 


k- 


— to'o- 

Plcm. 


Sec-Hon — A-B. 
Fig.    44. — Portable   Wooden    Panels   for  Covering  Floors. 

the  center,  these  pipes  discharging  live  steam  through  open- 
ings into  the  enclosed  space.  In  addition  to  the  steam  piping 
10  braziers  in  which  coke  fires  were  kept  were  scattered 
around  the  floor.  This  equipment  kept  the  enclosed  story, 
50  x  100  ft.  x  13  ft.  high,  at  a  temperature  of  80°  F.  and  at  tem- 
perature of  about  40°  F.  between  the  floor  top  and  its  board 
covering.  The  work  was  not  stopped  at  any  time  because  of 
cold  and  the  temperatures  outside  ranged  from  zero  to  10° 
above. 


CHAPTER    VIII. 

METHODS   AND   COST   OF    FINISHING   CONCRETE 

SURFACES. 

Good  design  in  concrete  as  well  as  in  steel,  masonry  and 
wood,  requires  that  the  structure  shall  be  good  to  look  at. 
This  means  that  the  proportions  must  be  good  and  that  the 
surface  finish  must  be  pleasing.  Good  proportions  are  a  mat- 
ter of  design  but  a  pleasing  surface  finish  is  a  matter  of  con- 
struction. Many,  perhaps  the  majority  of,  concrete  structures 
do  not  have  a  pleasing  surface  finish ;  the  surface  is  irregular, 
uneven  in  texture,  and  stained  or  discolored  or  of  lifeless  hue. 
The  reasons  for  these  faults  and  the  possible  means  of  remedy- 
ing them  are  matters  that  concern  the  construction  engineer 
and  the  contractor. 

Imperfections  in  the  surface  of  concrete  are  due  to  one  or 
more  of  the  following  causes:  (i)  Imperfectly  made  forms; 
(2)  imperfectly  mixed  concrete;  (3)  carelessly  placed  con- 
crete; (4)  use  of  forms  with  dirt  or  cement  adhering  to  the 
boards;  (5)  efflorescence  and  discoloration  of  the  surface  after 
the  forms  are  removed. 

IMPERFECTLY  MADE  FORMS.— In  well  mixed  and 
placed  concrete  the  film  of  cement  paste  which  flushes  to  the 
surface  will  take  the  impress  of  every  flaw  in  the  surface  of 
the  forms.  It  will  even  show  the  grain  marks  in  well  dressed 
lumber.  From  this  it  will  be  seen  how  very  difficult  it  is  so  to 
mold  concrete  that  the  surface  will  not  bear  evidence  of  the 
mold  used.  The  task  is  impracticable  of  perfect  accomplish- 
ment and  the  degree  of  perfection  to  which  it  can  be  carried 
depends  upon  the  workmanship  expended  in  form  construc- 
tion. Forms  with  a  smooth  and  even  surface  are  difficult  and 
expensive  to  secure.  It  is  impracticable  in  the  first  place  to 
secure  lagging  boards  dressed  to  exact  thickness  and  in  the 
second  place  it  is  impracticable  to  secure  perfect  carpenter 
work ;  joints  cannot  be  got  perfectly  close  and  a  nail  omitted 

124 


FINISHING    CONCRETE   SURFACES.  125 

here  or  there  leaves  a  board  free  to  warp.  From  this  point  on 
the  use  of  imperfectly  sized  lumber  and  careless  carpentry  can 
go  to  almost  any  degree  of  roughness  in  the  form  work.  Only 
approximately  smooth  and  unmarked  concrete  surfaces  can  be 
secured  in  plain  wooden  forms  and  this  only  with  the  very 
best  kind  of  form  construction.  So  much  for  the  limitations 
of  form  work  in  the  matter  of  securing  surface  finish.  These 
limitations  may  be  reduced un  various  ways.  Joint  marks  may 
be  eliminated  wholly  or  partly  by  pointing  the  joints  with 
clay  or  mortar  or  by  pasting  strips  of  paper  or  cloth  over  them, 
or  the  whole  surface  of  the  lagging  can  be  papered ;  by  the 
use  of  oiled  paper  there  will  be  little  trouble  from  the  paper 
sticking.  Grain  marks  and  surface  imperfections  can  be  re- 
duced by  oiling  the  lumber  so  as  to  fill  the  pores  or  by  first 
oiling  and  then  filling  the  coat  of  oil  with  fine  sand  blown 
or  cast  against  the  boards. 

The  preceding  remarks  are  of  course  based  on  the  assump- 
tion that  as  nearly  as  possible  a  smooth  and  even  surface 
finish  is  desired.  If  something  less  than  this  is  sufficient,  and 
in  many  cases  it  is,  form  produced  surface  defects  become 
negligible  in  the  proportion  that  they  do  not  exceed  the  stan- 
dards of  roughness  and  irregularity  considered  permissible  by 
the  engineer  and  these  standards  are  individual  with  the 
engineer;  what  one  considers  excessive  roughness  and  irregu- 
larity another  may  consider  as  amply  even  and  smooth.  The 
point  to  be  kept  in  mind  is  that  beyond  a  certain  state  of 
evenness  and  regularity  form  produced  surfaces  are  impracti- 
cable to  obtain,  because  to  construct  forms  of  the  necessary 
perfection  to  obtain  them  costs  far  more  than  it  does  to  em- 
ploy special  supplementary  finishing  processes. 

Surface  blemishes  due  to  dirt  or  cement  adhering  to  the 
form  boards  have  no  excuse  if  the  engineer  or  contractor  cares 
to  avoid  them.  It  is  a  simple  matter  to  keep  the  lagging  clean 
and  free  from  such  accumulations. 

IMPERFECT  MIXING  AND  PLACING.— Imperfectly 
mixed  and  placed  concrete  gives  irregularly  colored,  pitted 
and  honeycombed  surfaces  with  here  a  patch  of  smooth 
mortar  and  there  a  patch  of  exposed  stone.  Careful  mixing 
and  placing  will  avoid  this  defect,  or  all  chance  of  it  may  be 
eliminated  by  using  surface  coatings  of  special  mixtures. 


126  CONCRETE    CONSTRUCTION. 

There  is  no  great  difficulty,  however,  in  obtaining  a  reason- 
ably homogeneous  surface  with  concrete ;  the  task  merely 
requires  that  the  mixing  shall  be  reasonably  uniform  and 
homogeneous  and  that  in  placing  this  mixture  the  spading 
next  to  the  lagging  shall  be  done  in  such  a  way  as  to  pull 
the  coarse  stones  back  and  flush  the  mortar  to  the  surface. 
Spading  forks  are  excellent  for  this  purpose.  A  better  tool  is 
a  special  spade  made  with  a  perforated  blade;  this  special 
spade  costs  $3. 

EFFLORESCENCE. — Efflorescence  is  the  term  applied  to 
the  whitish  or  yellowish  accumulations  which  often  appear 
on  concrete  surfaces.  "Whitewash"  is  another  name  given  to 
these  blotches.  Efflorescence  is  due  to  certain  salts  leaching 
out  of  the  concrete  and  accumulating  into  thin  layers  where 
the  water  evaporates  on  the  surface.  These  salts  are  most 
probably  sulphates  of  calcium  and  magnesium,  both  of  which 
are  contained  in  many  cements  and  both  of  which  are  slightly 
soluble  in  water.  Efflorescence  is  very  erratic  in  its  appear- 
ance. Some  concretes  never  exhibit  it ;  in  some  it  may  not 
appear  for  several  years,  and  in  others  it  shows  soon  after 
construction  and  may  appear  in  great  quantities.  The  most 
effective  way  to  prevent  efflorescence  would  naturally  be  to 
use  cements  entirely  free  from  sulphates,  chlorides  'or  what- 
ever other  soluble  salts  are  the  cause  of  the  phenomenon,  but 
the  likelihood  of  engineers  resorting  to  the  trouble  of  such 
selection,  except  in  rare  instances,  is  not  great,  even  if  they 
knew  what  cements  to  select,  so  that  other  means  must  be 
sought.  The  most  common  place  for  efflorescence  to  appear  in 
walls  is  at  the  horizontal  junction  of  two  days'  work  or  where 
a  coping  is  placed  after  the  main  body  of  the  wall  has  been 
completed.  The  reason  of  this  seems  to  be  that  the  salt  solu- 
tions ,seep  down  through  the  concrete  until  they  strike  the 
nearly  impervious  film  of  cement  that  forms  on  the  top  surface 
of  the  old  concrete  before  the  new  is  added,  and  then  they 
follow  along  this  impervious  film  to  the  face  of  the  wall.  The 
authors  have  suggested  that  this  cause  might  be  remedied  by 
ending  the  day's  work  by  a  layer  whose  top  has  a  slight  slope 
down  toward  the  rear  of  the  wall  or  perhaps  by  placing  all 
the  concrete  in  similarly  sloping  layers.  Mr.  C.  H.  Cartlidge 
is  authority  for  the  statement  that  this  leaching  at  joints  can 


FINISHING   CONCRETE   SURFACES.  127 

be  largely  done  away  with  by  the  simple  process  of  washing 
the  top  surface  of  concrete  which  has  been  allowed  to  set  over 
night  by  scrubbing  it  with  wire  brushes  in  conjunction  with 
thorough  flushing  with  a  hose.  But  efflorescence  frequently 
appears  on  the  faces  of  walls  built  without  construction  joints 
and  in  which  a  wet  concrete  is  puddled  in  and  not  tamped  in 
layers,  and  here  other  means  are  obviously  essential.  Water- 
proofing the  surface  of  the  wall  should  be  effective  so  long 
as  the  waterproofing  lasts ;  indeed  one  of  the  claims  made  for 
some  of  these  waterproofing  compounds  is  that  efflorescence  is 
prevented.  The  various  waterproofing  mixtures  capable  of 
such  use  will  be  found  described  in  Chapter  XXV.  Failing 
in  any  or  all  of  these  methods  of  preventing  efflorescence  the 
engineer  must  resort  to  remedial  measures.  The  saline  coating 
must  be  scraped,  or  chipped,  or  better,  washed  away  with 
acids. 

Efflorescence  was  removed  from  a  concrete  bridge  at  Wash- 
ington, D.  C.,  by  using  hydrochloric  (muriatic)  acid  and  com- 
mon scrubbing  brushes ;  30  gals,  of  acid  and  36  scrubbing 
brushes  were  used  to  clean  250  sq.  yds.  of  concrete.  The  acid 
was  diluted  with  4  or  5  parts  water  to  I  of  acid ;  water  was 
constantly  played  with  a  hose  on  the  concrete  while  being 
cleaned  to  prevent  penetration  of  the  acid.  One  house-front 
cleaner  and  5  laborers  were  employed,  and  the  total  cost  was 
$150,  or  60  cts.  per  sq.  yd.  This  high  cost  was  due  to  the 
difficulty  of  cleaning  the  balustrades.  It  is  thought  that  the 
cost  of  cleaning  the  spandrels  and  wing  walls  did  not  exceed 
.20  cts.  per  sq.  yd.  The  cleaning  was  perfectly  satisfactory. 
An  experiment  was  made  with  wire  brushes  without  acid,  but 
the  cost  was  $2.40  per  sq.  yd.  The  flour  removed  by  the  wire 
brushes  was  found  by  analysis  to  be  silicate  of  lime.  Acetic 
acid  was  tried  in  place  of  muriatic,  but  required  more 
scrubbing. 

SPADED  AND  TROWELED  FINISHES.— With  wet- 
concrete  and  ordinarily  good  form  construction  a  reasonably 
good  surface  appearance  can  be  obtained  by  spading  and  trow- 
eling. For  doing  the  spading  a  common  gardener's  hoe, 
straightened  out  so  that  the  blade  is  nearly  in  line  with  the 
handle  will  do  good  work.  The  blade  of  the  tool  is  pushed 
down  next  to  the  lagging  and  the  stone  pulled  back  giving  the 


128  CONCRETE    CONSTRUCTION. 

grout  opportunity  to  flush  to  the  face.  Troweling,  that  is 
troweling  without  grout  wash,  requires,  of  course,  that  the 
concrete  be  stripped  before  it  has  become  too  hard  to  be 
worked.  As  troweling  is  seldom  required  except  for  tops  of 
copings  and  corners  it  is  generally  practicable  to  bare  the 
concrete  while  it  is  still  fairly  green.  In  this  condition  the 
edges  of  copings,  etc.,  can  be  rounded  by  edging  tools  such 
as  cement  sidewalk  workers  use. 

PLASTER  AND  STUCCO  FINISH.— The  ordinary  con- 
crete surface  with  a  film-like  cement  covering  will  not  hold 
plaster  or  stucco.  To  get  proper  adhesion  the  concrete  sur- 
face must  be  scrubbed,  treated  with  acid  or  tooled  before  the 
plaster  or  stucco  is  applied  and  this  makes  an  expensive  finish 
since  either  of  the  preliminary  treatments  constitutes  a  good 
finish  by  itself.  When  a  coarse  grained  facing  is  made  of  very 
dry  mixtures,  as  described  in  a  succeeding  section,  it  has  been 
made  to  hold  plaster  very  well  on  inside  work.  In  general 
plaster  and  stucco  finishes  can  be  classed  as  uncertain  even 
when  the  concrete  surface  has  been  prepared  to  take  them, 
and  when  the  concrete  has  not  been  so  prepared  such  finishes 
can  be  classed  as  absolutely  unreliable. 

MORTAR  AND  CEMENT  FACING.— Where  a  surface 
finish  of  fine  texture  or  of  some  special  color  or  composition  is 
desired  the  concrete  is  often  faced  with  a  coat  of  mortar  or, 
sometimes,  neat  cement  paste  or  grout.  Mortar  facing  is  laid 
from  I  to  2  ins.  thick,  usually  il/2  ins.,  the  mortar  being  a  i-i, 
1-2  or  1-3  mixture  and  of  cement  and  ordinary  sand  where  no 
special  color  or  texture  is  sought.  This  facing  often  receives 
a  future  special  finish  as  described  in  succeeding  sections,  bu; 
it  is  more  usually  used  as  left  by  the  forms  or  at  best  with 
only  a  troweling  or  brushing  with  grout.  Engineers  nearly 
always  require  that  the  mortar  facing  and  the  concrete  back- 
ing shall  be  constructed  simultaneously.  This  is  accomplished 
by  using  facing  forms,  two  kinds  of  which  are  shown  by  Figs. 
45  and  46.  In  use  the  sheet  steel  plates  are  placed  on  edge 
the  proper  distance  back  of  the  lagging  and  the  space  between 
them  and  the  lagging  is  filled  with  the  facing  mortar.  The 
concrete  backing  is  then  filled  in  to  the  height  of  the  plate, 
which  is  then  lifted  vertically  and  the  backing  and  facing  thor- 
oughly bonded  by  tamping  them  together.  The  form  shown 


FINISHING    CONCRETE   SURFACES.  129 

by  Fig.  46,  though  somewhat  the  more  expensive,  is  the  prefer- 
able one,  since  the  attached  ribs  keep  the  plate  its  exact  dis- 
tance from  the  lagging  without  any  watching  by  the  men, 
while  the  flare  at  the  top  facilitates  rilling.  The  facing  mortar 
has  to  be  rather  carefully  mixed;  it  must  be  wet  enough  to 
work  easily  and  completely  into  the  narrow  space  and  yet  not 
be  so  soft  that  in  tamping  the  backing  the  stones  are  easily 
forced  through  it.  Also  since  the  facing  cannot  proceed  faster 

?fy8 'hole 


Plate  to  be  3/is'  thick 


-   8  feet 

Eng.-Contr  Hook  for  removing 

plate 

Fig.   45. — Form  for  Applying-  Cement  Facing  (Massachusetts  Highway  Com- 
mission). 

than  the  backing  the  mortar  has  to  be  mixed  in  small  batches 
so  that  it  is  always  fresh.  A  cubic  yard  of  mortar  will  make 
216  sq.  ft.  of  1^2-in.  facing.  Cement  facing  is  seldom  made 
more  than  i  in.  thick.  If  placed  as  a  paste  the  process  is 
essentially  the  same  as  for  placing  mortar.  When  grout  is 
used  a  form  is  not  used ;  place  and  tamp  the  concrete  in  6  to 
8-in  layers,  then  shove  a  common  gardener's  spade  down  be- 


Eng.-Contr, 


Fig.   46.— Form  for  Applying  Cement  Facing  (Illinois  Central  R.  R.). 

tween  the  concrete  and  the  lagging  and  pull  back.the  concrete 
about  an  inch  and  pour  the  opening  full  of  grout  and  with- 
draw the  spade.  If  this  work  is  carefully  done  there  will  be 
very  few  stones  showing  when  the  forms  are  removed.  When 
stiff  pastes  or  mortars  are  used  the  contractor  often  places  the 
facing  by  plastering  the  lagging  just  ahead  of  the  concreting; 
this  process  requires  constant  watching  to  see  that  the  plaster 


I3o  CONCRETE    CONSTRUCTION. 

coat  does  not  slough  or  peel  off  before  it  is  backed  up  with 
concrete. 

SPECIAL  FACING  MIXTURES  FOR  MINIMIZING 
FORM  MARKS. — The  ordinary  facing  mixture  of  mortar  or 
cement  is  so  fine  grained  and  plastic  that  it  readily  takes  the 
impress  of  every  irregularity  in  the  form  lagging;  where  a 
particularly  good  finish  is  desired  this  makes  necessary  subse- 
quent finishing  treatments.  To  avoid  these  subsequent  treat- 
ments and  at  the  same  time  to  reduce  the  form  marks,  special 
facing  mixtures,  which  will  not  take  the  imprint  of  and  which 
will  minimize  rather  than  exaggerate  every  imperfection  in 
the  forms,  have  been  used  with  very  considerable  success  in 
the  concrete  work  done  for  the  various  Chicago,  111.,  parks. 
The  mixture  used  consists  usually  of  I  part  cement,  3  parts 
fine  limestone  screenings  and  3  parts  ^-in.  crushed  limestone ; 
these  materials  are  mixed  quite  dry  so  no  mortar  will  flush  to 
the  surface  when  rammed  hard.  With  moderately  good  form 
work  the  imprint  of  the  joints  is  hardly  noticeable  and  grain 
marks  do  not  show  at  all.  For  thin  building  walls  the  special 
mixture  is  used  throughout  the  wall,  but  for  more  massive 
structures  it  is  used  only  for  the  facing. 

GROUT  WASHES.— Grout  finishes  serve  only  to  fill  the 
small  pits  and  pores  in  the  surface  coating;  cavities  or  joint 
lines,  if  any  exist,  must  be  removed  by  plastering  or  rubbing 
before  the  grout  is  applied  or  else  by  applying  the  grout  by 
rubbing.  In  ordinary  work  the  grout  is  applied  with  a  brush 
after  the  holes  have  been  plastered  and  the  joint  marks  rubbed 
down.  The  grout  to  be  applied  with  a  brush  should  be  about 
the  consistency  of  whitewash ;  a  I  cement  2  sand  mixture  is 
a  good  one.  Where  a  more  perfect  finish  of  dark  color  is 
desired  the  grout  of  neat  cement  and  lampblack  in  equal  parts 
may  be  applied  as  follows:  Two  coats  with  a  brush,  the 
second  coat  after  the  first  has  dried,  and  one  coat  by  sweeping 
with  a  small  broom.  The  broom  marks  give  a  slightly  rough 
surface.  Instead  of  a  liquid  grout  a  stiff  grout  or  semi-liquid 
mortar  applied  with  a  trowel  or  float  can  be  used.  In  this  case 
the  grout  should  be  applied  in  a  very  thin  coat  and  troweled 
or  floated  so  that  only  the  pores  are  filled  and  no  body  of 
mortar  left  on  the  surface  or  else  it  will  scale  off.  A  more 
expensive  but  very  superior  grout  finish  is  obtained  by  rub- 


FINISHING    CONCRETE    SURFACES. 


bing  and  scouring  the  wet  grout  into  the  surface  with  cement 
mortar  bricks,  carborundum  bricks,  or  such  like  abrasive  ma- 
terials. A  I  cement  J  sand  mortar  brick,  with  a  handle 
molded  into  it,  and  having  about  the  dimensions  of  an  ordi- 
nary building  brick  makes  a  good  tool  for  rubbing  down 
joint  marks  as  well  as  for  applying  grout. 

FINISHING  BY  SCRUBBING  AND  WASHING.— A 
successful  finish  for  concrete  structures  consists  in  removing 
the  forms  while  the  concrete  is  green  and  then  scrubbing  the 

^ surface  with  a  brush  and 

water  until  the  film  of 
cement  is  removed  and 
the  clean  sand  or  stone 
left  exposed.  This  meth- 
od has  been  chiefly  used 
in  concrete  work  done  by 
the  city  of  Philadelphia, 
Pa.,  Mr.  Henry  M.  Quim- 
by,  Bridge  Engineer.  Fig- 
ure 47  shows  an  example 
of  scrubbed  finish,  but  of 
course  the  texture  or 
color  of  the  surface  will 
vary  with  the  character 
of  the  face  mixture  and 
the  hue  of  the  sand  or 
chips  used.  Warm  tones 
can  be  secured  by  the  use 
of  crushed  brick  or  red 
gravel ;  a  dark  colored 
stone  with  light  sand 
gives  a  color  much  re- 
sembling granite;  fine 
gravel  or  coarse  sand 
gives  a  texture  like  sand- 
stone. In  much  of  this 
work  done  in  Philadel- 
phia a  mixture  composed  of  i  part  cement,  2  parts  bank  sand 
and  3  parts  crushed  and  cleaned  black,  slaty  shale  from  ^  to 
*4  in.  in  size,  has  been  used  with  good  results  both  in  appear- 


Fig.  47.— Concrete  Baluster  Finished 

by  Scrubbing  and  Washing. 


132  CONCRETE    CONSTRUCTION. 

ance  and  in  durability.  The  scrubbing  is  done  with  an  ordi- 
nary house  scrubbing  brush  at  the  same  time  flushing  the  con- 
crete with  water  from  a  sponge  or  bucket  or,  preferably,  from* 
a  hose.  In  general  the  washing  is  done  on  the  day  following 
the  placing  of  the  concrete  but  the  proper  time  depends  upon 
the  rapidity  with  which  the  concrete  sets.  In  warm  weather 
'24  hours  after  placing  is  generally  about  right,  but  in  cold 
weather  48  hours  may  be  required,  and  in  very  cold  weather 
the  concrete  has  been  left  to  set  a  week  and  the  scrubbing 
has  been  successful.  With  the  concrete  in  just  the  proper 
condition  a  few  turns  of  the  brush  with  plenty  of  water  will 
clean  away  the  cement,  but  if  a  little  too  hard  wire  brushes 
must  be  used  and  if  still  harder  a  scouring  brick  or  an  ordinary 
brick  with  sand  is  necessary  to  cut  the  cement  film.  The 


Fig.    48. — Concrete   Abutment  with   Scrubbed   Finish    and  Course  Marks. 

process  requires  that  the  forms  shall  be  so  constructed  that 
the  lagging  can  be  removed  when  the  concrete  has  reached  the 
proper  age  for  treatment.  Mr.  Quimby  sets  the  studs  8  to  12 
ins.  from  the  face  and  braces  the  lagging  boards  against  them 
by  cleats  nailed  so  as  to  be  easily  loosened.  His  practice  is  to 
use  boards  in  one  width  the  full  depth  of  the  course  and  to 
nail  a  triangular  bead  strip  to  the  face  at  each  edge.  These 
bead  strips  mark  the  joints  between  courses  as  shown  by 
Fig.  48.  When  a  "board"  is  taken  off  it  is  cleaned  and  oiled 
and  reset  for  a  new  course  by  inserting  the  bottom  bead  strip 
in  the  half  indentation  left  by  the  top  bead  in  the  concrete. 
This  is,  of  course,  for  work  of  such  size  that  one  course  is  a 
day's  work  of  concreting.  In  such  work,  two  carpenters  with 


FINISHING    CONCRETE    SURFACES.  133 

perhaps  one  helper  will  remove  a  course  of  "boards"  say  100  ft. 
long  in  from  4  to  8  hours.  While  forms  of  the  kind  described 
cost  more  to  construct  there  is  a  saving  by  repeated  re-use 
of  the  lagging  boards.  The  indentations  or  beads  marking  the 
courses  serve  perfectly  to  conceal  the  construction  joints. 
The  cost  of  scrubbing  varies  with  the  hardness  of  the  con- 
crete ;  when  in  just  the  right  condition  for  effective  work  one 
man  can  scrub  100  sq.  ft.  in  an  hour ;  on  the  other  hand  it  has 
taken  one  man  a  whole  day  to  scrub  and  scour  the  same  area 
when  the  concrete  was  allowed  to  get  hard. 

FINISHING  BY  ETCHING  WITH  ACID.— The  acid 
etched  or  acid  wash  process  of  finishing  concrete  consists  in 
first  washing  the  surface  with  an  acid  preparation  to  remove 
the  surface  cement  and  expose  the  sand  and  stone,  then  with 
an  alkaline  solution  to  remove  all  free  acid,  and  finally,  with 
clear  \vater  in  sufficient  volume  to  cleanse  and  flush  the  sur- 
face thoroughly.  The  work  can  be  done  at  any  time  after  the 
forms  are  removed  and  does  not  require  skilled  labor;  any 
man  with  enough  judgment  to  determine  when  the  etching  has 
progressed  far  enough  can  do  the  wrok.  This  process  has 
been  very  extensively  used  in  Chicago  by  the  South  Park 
Commission,  Mr.  Linn  White,  Engineer.  In  this  work  the 
concrete  is  faced  with  a'  mixture  of  cement,  sand  and  stone 
chips,  any  stone  being  used  that  is  not  affected  by  acid. 
Limestone  is  excluded.  Where  some  color  is  desired  the 
facing  can  be  mixed  with  mineral  pigments  or  with  colored 
sand  or  stone  chips.  This  acid  wash  process  has  been  pat- 
ented, the  patentees  being  represented  by  Mr.  J.  K.  Irvine, 
Sioux  City,  la. 

TOOLING  CONCRETE  SURFACES.— Concrete  surfaces 
may  be  bush-hammered  or  otherwise  tool  finished  like  natural 
stone,  exactly  the  same  methods  and  tools  being  used.  Tool- 
ing must  wait,  however,  until  the  concrete  has  become'  fairly 
hard.  As  the  result  of  his  experience  in  tooling  some  43,000 
sq.  ft.  of  concrete,  Mr.  W.  J.  Douglas  states  that  the  concrete 
should  be  at  least  30  days  old  and,  preferably,  60  days  old,  if 
possible,  when  bush-hammered.  There  is  a  great  variation  in 
the  costs  given  for  tooling  concrete.  Mr.  C.  R.  Neher  states 
that  a  concrete  face  can  be  bush-hammered  by  an  ordinary 
laborer  at  the  rate  of  100  sq.  ft.  in  10  hours  or  at  a  cost  of 


134  CONCRETE    CONSTRUCTION. 

il/2  cts.  per  square  foot  with  wages  at  15  cts.  per  hour.  Mr. 
E.  L.  Ransome  states  that  bush-hammering  costs  from  il/2  to 
2l/2  cts.  per  square  foot,  wages  of  common  laborers  being  15 
cts.  per  hour.  The  walls  of  the  Pacific  Borax  Co.'s  factory  at 
Bayonne,  N.  J.,  were  dressed  by  hand  at  the  rate  of  100  to  200 
sq.  ft.  per  man  per  day;  using  pneumatic  hammer  one  man 
was  able  to  dress  from  300  to  600  sq.  ft.  per  day.  In  construct- 
ing the  Harvard  Stadium  the  walls  were  dressed  with  pneu- 
matic hammers  fitted  with  a  tool  with  a  saw-tooth  cutting 
blade  like  an  ice  chopper.  Men  timed  by  one  of  the  authors  on 
a  visit  to  this  work  were  dressing  wall  surface  at  the  rate  OL 
50  sq.  ft.  per  hour,  but  the  con-tractor  stated  that  the  average 
work  per  man  per  day  was  200  sq.  ft.  Common  laborers  were 
employed.  The  average  cost  of  bush-hammering  some  43,000 
sq.  ft.  of  plain  and  ornamental  blocks  for  the  Connecticut  Ave- 
nue Bridge  at  Washington,  D.  C,  was  26  cts.  per  square  foot. 
Both  pneumatic  tools  and  hand  tooling  were  employed  and 
the  work  of  both  is  lumped  in  the  above  cost,  but  hand  tooling 
cost  about  twice  as  much  as  machine  tooling.  The  work  was 
done  by  high-priced  men,  foremen  stone  cutters  at  $5  per  day 
and  stone  cutters  at  $4  per  day.  Moreover  a  grade  of  work 
equal  to  the  best  bush-hammered  stone  work  was  demanded. 
Full  details  of  the  cost  of  this  work  are  given  in  Chapter 
XVII.  Mr.  H.  M.  Quimby  states  that  the  cost  of  tooling  con- 
crete runs  from  3  cts.  to  12  cts.  per  square  foot,  according  to 
the  character  and  extent  of  the  work  and  the  equipment. 

GRAVEL  OR  PEBBLE  SURFACE  FINISH.— An  effect- 
ive variation  of  the  ordinary  stone  concrete  surface  is  secured 
by  using  an  aggregate  of  rounded  pebbles  of  nearly  uniform 
size  and  by  scrubbing  or  etching" remove  the  cement  enough 
to  leave  the  pebbles  about  half  exposed  at  the  surface.  In 
constructing  a  bridge  at  Washington,  D.  C.,  the  concrete  was 
a  1-2-5  gravel  mixture  of  il/2  to  2-in.  pebbles  for  the  spandrels 
and  arch  ring  face  and  of  i-in.  pebbles  for  the  parapet  walls. 
The  forms  were  removed  while  the  concrete  was  still  green 
and  the  cement  scrubbed  from  around  the  faces  and  sides  of 
the  pebbles  using  wire  brushes  and  water.  Tests  showed  that 
at  12  hours  age  the  concrete  was  not  hard  enough  to  prevent 
the  pebbles  from  being  brushed  loose  and  that  at  36  hours 
age  it  was  too  hard  to  permit  the  mortar  to  be  scrubbed  away 


FINISHING    CONCRETE   SURFACES.  135 

without  excessive  labor ;   the  best  results  were  obtained  when 
the  concrete  was  about  24  hours  old. 

COLORED  FACING.— Where  occasion  calls  for  concrete 
of  a  color  or  tint  other  than  is  obtained  by  the  use  of  the  ordi- 
nary materials  either  an  aggregate  of  a  color  suitable  for  the 
purpose  may  be  used  or  the  mixture  may  be  colored  by  the 
addition  of  some  mineral  pigment.  The  first  method  is  by  all 
odds  the  preferable  one ;  it  gives  a  color  which  will  endure  for 
all  time  and  it  in  no  way  injures  the  strength  or  durability  of 
the  concrete.  Mineral  pigments  may  be  secured  from  any  of 
several  well-known  firms  who  make  them  for  coloring  con- 
crete, and  they  may  be  had  in  almost  every  shade.  Directions 
for  using  these  colors  can  be  had  from  the  makers.  All  but  a 
very  few  of  these  mineral  colors  injure  the  strength  and  dura- 
bility of  the  concrete  if  used  in  amounts  sufficient  to  produce 
the  desired  color  and  all  of  them  fade  in  time.  The  best 
method  of  producing  a  colored  mortar  or  concrete  facing  is  to 
mix  the  cement  with  screenings  produced  by  crushing  a 
natural  stone  of  the  desired  color. 


CHAPTER  IX. 
METHODS  AND  COST  OF  FORM  CONSTRUCTION. 

Concrete  being  a  plastic  material  when  deposited  requires 
molds  or  forms  to  give  it  the  shape  required  and  to"  maintain 
it  in  that  shape  until  it  has  hardened  to  sufficient  strength  to 
require  no  exterior  support.  The  material  used  in  construct- 
ing forms  is  wood.  Beyond  the  use  of  metal  molds  for  build- 
ing blocks  for  sewer  construction  and  for  ornamental  and 
a  few  architectural  shapes,  iron  and  steel  are  used  in  form 
construction  only  as  ties  and  clamps  to  hold  parts  of  wood 
forms  together — except  in  rare  instances.  A  discussion  of 
form  construction,  therefore,  is  essentially  a  discussion  of 
wood  forms. 

Before  taking  up  this  discussion,  however,  attention  de- 
serves to  be  called  to  the  opportunities  for  the  development  of 
metal  forms.  Lumber  is  costly  and  is  growing  more  scarce 
and  costly  all  the  time.  A  substitute  which  can  be  repeatedly 
used  and  whose  durability  and  salvage  value  are  great  pre- 
sents itself  in  steel  if  only  a  system  of  form  units  can  be 
devised  which  is  reasonably  adjustable  to  varying  conditions. 
Cylindrical  steel  column  molds  have  been  used  to  some  extent 
and  are  discussed  in  Chapter  XIX.  In  Chapter  XVI  we 
describe  a  steel  form  for  side  walls  of  a  tunnel  lining.  In 
some  building  work  done  in  the  northwest  corrugated  steel 
panels  or  sheets  have  been  used  as  lagging  for  floor  slab  cen- 
ters. A  number  of  styles  of  metal  forms  or  centers  for  sewer 
and  tunnel  work  have  been  devised  and  used  and  are  discussed 
in  Chapter  XXI.  Despite  this  considerable  use  of  metal  for 
special  forms  nothing  approaching  its  general  use  like  wood 
has  been  attempted,  and  the  field  lies  wide  open  for  invention. 

The  economics  of  form  construction  deserve  the  most  seri- 
ous attention  of  the  engineer  and  contractor.  It  is  seldom  that 
form  work,  outside  of  very  massive  foundation  construction, 
costs  less  than  50  cts.  per  cubic  yard  of  concrete  in  place,  and 

136 


FORM    COXSTRUCTIOK.  137 

it  is  not  unusual  in  the  more  complex  structures  for  it  to  cost 
$5  per  cubic  yard  of  concrete  in  place.  These  costs  include 
the  cost  of  materials  and  of  framing,  handling  and  removing 
the  forms  but  they  do  not  embrace  extremely  high  or  low 
costs.  It  is  evident  without  further  demonstration  that  time 
spent  in  planning  economic  form  construction  for  any  consid- 
erable job  of  concrete  work  is  time  spent  profitably. 

In  the  following  sections  we  review  the  general  considera- 
tions which  enter  into  all  form  work.  Specific  details  of  con- 
struction and  specific  costs  of  form  work  are  given  in  succeed- 
ing chapters  where  each  class  of  concrete  work  is  discussed 
separately.  This  chapter  is  intended  principally  to  familiarize 
the  reader  with  general  principles  governing  form  work. 

EFFECT  OF  DESIGN  ON  FORM  WORK.— The  design- 
ing engineer  can  generally  aid  largely  in  reducing  the  cost 
of  form  work  if  he  will.  This  is  particularly  true  in  building 
work  in  which,  also,  form  costs  run  high.  By  arranging  his 
beam  spacing  and  sizes  with  a  little  care  he  will  enable  the 
contractor  to  use  his  "forms  over  and  over  and  thus  greatly 
reduce  the  expense  for  lumber.  In  the  same  way  columns 
may  be  made  of  dimensions  which  will  avoid  frequent  re- 
making of  column  forms.  Panel  recesses  in  walls  may  be 
made  the  thickness  of  a  board  or  plank,  instead  of  some  odd 
depth  that  will  require  a  special  thickness  of  lumber,  or  beams 
may  be  made  of  such  size  that  certain  dimension  widths  of 
lumber  can  be  used  without  splitting.  In  general,  carpenter 
work  costs  more  than  concrete  and  where  a  little  excess  con- 
crete may  be  contributed  to  save  carpenter  work  it  pays  to 
contribute  it.  The  figures  given  in  Chapter  XIX,  showing  the 
reduction  in  lumber  cost  coming  from  using  the  same  material 
over  a  second  or  third  time,  should  be  studied  in  this  connec- 
tion. The  leading  firms  of  engineering-contractors  which  both 
design  and  construct  reinforced  concrete  buildings  fully  realize 
these  opportunities  and  take  advantage  of  them,  but  the  gen- 
eral practitioner,  particularly  if  he  be  an  architect,  does  not 
do  so.  The  authors  have  personal  knowledge  of  one  building 
in  which  a  slight  change  in  spacing  and  dimensions  of  beams 
— a  change  that  would  have  been  of  no  architectural  or  struc- 
tural significance — would  have  reduced  the  successful  con- 
tractor's bid  for  the  work  by  $10,000.  The  designing  engineer 


138  CONCRETE    CONSTRUCTION. 

should  hold  it  as  a  cardinal  point  in  design  that  form  work, 
and  we  will  add  here  reinforcement  also,  should  so  far  as 
possible  be  made  interchangeable  from  bay  to  bay  and  from 
floor  to  floor. 

KIND  OF  LUMBER.— The  local  market  and  the  character 
of  the  work  generally  determine  the  kind  of  lumber  to  be  used 
for  forms.  The  hardwoods  are  out  of  the  question  for  form 
construction  because  they  cost  too  much  and  are  too  hard  to 
work.  Among  the  soft  woods  white  pine  costs  too  much  for 
general  use  and  hemlock  is  unreliable  when  exposed  to  the 
weather.  This  reduces  the  list  generally  available  to  spruce, 
Norway  pine  and  the  southern  pines.  Neither  green  nor  kiln- 
dried  lumber  is  so  good  as  partially  dry  stuff,  since  the  kiln- 
dried  lumber  swells  and  crushes  or  bulges  the  joints  and  green 
lumber  does  not  swell  enough  to  close  the  joints.  Forms  have 
to  withstand,  temporarily,  very  heavy  loads,  therefore,  knots, 
shakes  and  rot  must  be  watched  after.  The  choosing  of  good 
lumber  is  a  simple  process  and  the  contractor  who  wants  to 
be  able  to  rely  on  his  forms  will  look  after  it  carefully,  without 
going  to  extremes  which  the  work  does  not  warrant. 

FINISH  AND  DIMENSIONS  OF  LUMBER.— Dressing 
the  lumber  serves  four  important  purposes:  It  permits  tin* 
forms  to  be  constructed  more  nearly  true  to  line  and  surface : 
it  permits  tighter  joint  construction ;  it  gives  a  smoother  sur- 
face finish  to  the  concrete,  and  it  facilitates  the  removal  and 
cleaning  of  the  forms.  Undressed  lumber  may  be  used  for  the 
backs  of  walls  and  abutments,  for  work  below  ground  and 
wherever  a  smooth  and  true  surface  is  unimportant ;  there  are 
some  contractors,  however,  who  prefer  lumber  dressed  on 
one  side  even  for  these  purposes  because  of  the  smaller  cost 
of  cleaning.  For  floor  and  wall  forms  the  lumber  should 
always  be  dressed  on  one  side;  where  the  work  is  very  par- 
ticular both  sides  should  be  dressed,  and  in  special  cases  the 
sides  of  the  joists  or  studs  against  which  the'lagging  lies  may 
be  dressed.  For  ordinary  work  a  square  edge  finish  does  well 
enough  but  for  fine  face  work  a  tongue  and  groove  or 
bevel  edge  finish  is  preferable.  The  tongue  and  groove  finish 
gives  a  somewhat  tighter  joint  on  first  laying  but  it  does  not 
take  up  swelling  or  resist  wear  so  well  as  the  bevel  edge 
finish. 


FORM    CONSTRUCTION 


139 


When  ordering  new  lumber  for  forms  the  contractor  will 
save  much  future  work  and.  waste  if  he  does  it  from  plans. 
Timber  cut  to  length  and  width  to  go  directly  into  the  forms 
reduces  both  mill  and  carpenter  work  on  the  site,  and  in 
many  cases  it  can  be  so  ordered  if  ordered  from  plans.  Waste 
is  another  item  that  is  reduced  by  ordering  from  plans ;  with 
lumber  costing  its  present  prices  crop  ends  run  into  money 
very  rapidly.  When  old  lumber  from  a  previous  job  is  to  be 
used  the  contractor  can  only  make  the  best  of  his  stock,  but 
even  here  form  plans  will  result  in  saving.  Sort  and  pile  the 
old  lumber  according  to  sizes  and  make  a  schedule  of  the 
quantity  of  each  size  on  hand ;  this  schedule  in  the  hands  of 
the  man  who  designs  the  forms  and  of  the  head  carpenter  will 
materially  reduce  waste  and  carpenter  work.  It  is  ?ften 
possible  especially  in  making  concrete  foundations  for  frame 
buildings  to  use  lumber  for  forms  which  is  subsequently  used 
for  floor  beams,  etc.,  in  the  building. 

Contractors  differ  greatly  in  their  ideas  of  the  proper  thick- 
ness of  lumber  to  use  for  various  parts  of  form  work.  Gener- 
ally speaking  i%  to  2-in.  stuff  is  used  for  wall  lagging  held 
by  studding  and  i-in.  stuff  when  built  into  panels ;  for  floor 
lagging  i-in  stuff  with  joists  spaced  up  to  24  ins.  or  when 
built  into  panels;  for  column  lagging  \l/\  to  2-in.  stuff;  for 
sides  of  girders  i,  ij4,  il/2  and  2-in.  stuff  are  all  used;  and  for 
bottoms  of  girders,  il/2  and  2-in.  stuff.  These  figures  arc 
by  no  means  invariable  as  a  study  of  the  numerous  examples 
of  actual  form  work  given  throughout  this  book  will  show. 

COMPUTATION  OF  FORMS.— If  the  minimum  amount 
of  lumber  consistent  with  a  given  deflection  is  to  be  used  in 
form  work  the  sizes  and  spacing  of  the  supporting  members 
must  be  actually  computed  for  the  loading.  As  a  practical 
matter  of  fact  the  amount  of  material  used  and  the  arrange- 
ment of  the  supports  are  often  subject  to  requirements  of 
unit  construction,  clearance,  staging,  etc.,  which  supersede 
the  matter  of  economical  adaptation  of  material  to  loading. 
The  designing  of  form  work  is  at  best,  therefore,  a  compro- 
mise between  rules  of  thumb  and  scientific  calculation.  In 
wall  work  empirical  methods  are  nearly  always  followed.  In 
girder  and  floor  slab  work,  on  the  other  hand,  design  is  com- 
monly based  on  computation. 


I40  CONCRETE    CONSTRUCTION. 

In  the  matter  of  loads  the  general  practice  is  to  assume  the 
weight  of  concrete  as  a  liquid  at  some  amount  which  it  is 
considered  will  also  cover  the  weight  of  men,  barrows,  run- 
ways and  current  construction  materials.  The  assumed  weights 
vary.  One  prominent  engineering  firm  assumes  the  load 
to  be  the  dead  weight  of  concrete  as  a  liquid  and  the 
load  due  to  placing  and  specifies  that  the  forms  shall  be 
designed  to  carry  this  load  without  deflection.  Mr.  W. 
J.  Douglas,  Engineer  of  Bridges,  Washington,  D.  C,  as- 
sumes for  lateral  thrust  on  wrall  forms  that  concrete  is 
a  liquid  of  half  its  own  weight,  or  75  Ibs.  per  cu.  ft. 
Mr.  Sanford  E.  Thompson,  Consulting  Engineer,  Newton 
Highlands,  Mass.,  assumes  for  dead  load,  weight  of  concrete 
including  reinforcement  as  154  Ibs.  per  cu.  ft.,  and  for  live  load, 
75  Ibs.  per  sq.  ft.  on  slabs  and  50  Ibs.  per  sq.  ft.  in  figuring 
beam  and  girder  forms  and  struts. 

The'assumed  safe  stresses  in  form  work  may  be  taken  some- 
what higher  than  is  usual  in  timber  construction,  because  of 
the  temporary  character  of  the  load.  In  calculating  beams 
the  safe  extreme  fiber  stress  may  be  assumed  at  750  Ibs.  per 
sq.  in.  The  safe  stress  in  pounds  per  square  inch  for  struts 
or  posts  is  shown  by  Table  XV,  compiled  by  Mr.  Sanford  E. 
Thompson.  The  sizes  of  struts  given  are  those  most  com- 
monly used  in  form  work. 
Table  XV. — Safe  Strength  of  Timber  Struts  for  Frame  Work, 

—Dimensions  of  Strut. — 
Length  Strut.  3x4-^1.     4  x  4-in.     6x6-in.     8  x  8-in. 


Eeet. 

TJ. 

Lbs. 

Lbs, 

7OO 

Lbs. 

QOO 

Lbs. 

I  IOO 

12 

600 

/\j^ 

8OO 

I  OOO 

I  ^OO 

IO  ......... 

7OO 

QOO 

I  IOO 

I  2OO 

8  

8qo 

y^"~ 

I  CKO 

I  2OO 

I  2OO 

6  . 

I.  OCX) 

I.2OO 

I.2OO 

1.200 

In  using  this  table  it  must  be  borne  in  mind  that  bracing 
both  ways  reduces  the  length  of  a  long  strut.  For  example, 
if 'a  strut  24  ft.  long  be  divided  into  three  panels  by  bracing 
the  length  of  strut  so  far  as  the  table -is  concerned  is  8  ft. 

As  stated  above  wall  forms  are  rarely  computed.  Experi- 
ence has  shown  that  the  maximum  spans  of  various  thick- 
nesses of  lagging  between  supports  are:  i-in,  boards,  24  ins.; 


FORM    CONSTRUCTION. 


141 


i^-in,  plank,  4  ft.,  and  2-in.  plank,  5  ft.  Studding  will  vary 
in  size  from  2  x  4  to  4  x  6  ins.,  strutted  and  braced  horizontally 
to  meet  conditions.  Column  forms,  like  wall  forms,  are  rarely 
computed,  yokes  being  spaced  2  ft.  apart  for  ij/^-in.  lagging 
up  to  3  to  $l/2  ft.  apart  for  2-in.  lagging. 

Floor  forms,  including  girder  and  slab  forms,  are  computed 
on  the  basis  of  a  maximum  deflection  and  not  on  the  basis  of 
strength.  Sagging  forms  are  liable  to  rupture  the  beam  or 
slab.  The  amount  of  deflection  considered  allowable  varies 
from  no  deflection  up  to  %  to^  in.  Assuming  the  deflection, 
permissible  thickness  of  the  timber  necessary  to  carry  the  load 
is  determined  by  the  formulas : 

d=5   w  P+384  E  I (i) 

and 

bh* 
1  = (2) 

12 

Formula  (i)  is  the  familiar  one  for  computing  deflection  for 
a  beam  supported  (not  fixed)  at  the  ends.  Mr.  Sanford  E. 
Thompson  suggests  using  the  constant  3/384,  which  is  an  ap- 
proximate mean  between  1/384  that  for  beams  with  fixed  ends 
and  5/384  that  for  beams  with  ends  supported.  Formula  (i) 
then  becomes 

d=3  W  1*^384  E  I, 
in  which  as  above : 

c/=maximum  deflection  in  inches. 

PF=total  load  on  plank  or  joist. 

fclength  between  supports  in  inches. 

£=modulus  of  elasticity  of  lumber. 

7=moment  of  inertia  of  cross-section. 

b= breadth  of  lumber. 

h  =  depth  of  lumber. 

The  deflection,  d,  being  assumed  formula  (i)  is  solved  for 
I,  moment  of  inertia.  Substituting  the  value  of  /  in  formula 
(2)  we  can  readily  estimate  the  size  of  joist  or  thickness  of 
plank  to  use.  For  spruce,  yellow  pine  and  the  other  woods 
commonly  used  in  form  work  E  may  be  taken  equal  to  1,300,000 
Ibs.  per  sq.  in. 

DESIGN  AND  CONSTRUCTION.— The  main  points  to 
be  kept  in  mind  in  the  original  design  and  construction  of 
forms  are :  Economy  in  lumber,  economy  in  carpenter  work, 


I42  CONCRETE    CONSTRUCTION. 

and  economy  in  taking  down,  carrying  and  re-erecting.  Econ- 
omy in  lumber  is  not  merely  the  matter  of  using  the  least 
amount  of  lumber  that  will  serve  the  purpose  considering  the 
form  as  an  isolated  structure.  It  may  be  possible  to  build  a 
column  form,  for  example,  of  very  light  material  which  will 
serve  to  mold  a  single  column,  but  it  is  evident  that  we  could 
better  afford  to  use  twice  this  amount  of  lumber  if  by  doing 
so  we  obtained  a  form  which  could  be  used  over  again  to  mold 
a  second  column ;  no  more  lumber  per  column  would  be  used 
while  the  cost  of  erecting  a  form  already  framed  is  less  than 
the  cost  of  framing  a  new  form.  Economy  in  lumber  in  form 
construction  involves,  therefore,  recognition  of  the  economies 
to  be  gained  by  repeated  use  of  the  lumber.  A  certain  amount 
of  additional  sturdiness  is  required  in  the  shape  of  heavier 
form  lumber  and  stronger  framing  to  provide  for  the  wear 
and  tear  of  repeated  use,  and  it  is  always  economy  to  provide 
it  when  repeated  use  is  possible.  The  thing  can  be  overdone, 
however;  there  is  an  economical  limit  to  repeated  use,  as  we 
demonstrate  further  on.  In  the  matter  of  economy  in  car- 
penter work,  a  certain  amount  of  extra  work  put  into  framing 
the  forms  to  withstand  the  stress  of  repeated  use  is  economic- 
ally justifiable.  Also  carpenter  work  put  into  framing  which 
substitutes  clamps  and  wedges  for  nails  is  sound  economy ; 
generally  speaking  a  skillful  form  carpenter  is  recognized  by 
the  scarcity  of  nails  he  uses.  The  possibility  of  reducing 
carpenter  work  by  ordering  lumber  to  length  and  width  from 
plans  has  already  been  mentioned.  It  is  possible  often  to  go  a 
step  further  by  having  certain  standard  panels,  boxes,  etc.. 
made  in  regular  shops.  Piece  work  is  often  possible  and 
will  frequently  reduce  framing  costs.  In  designing  for  econ- 
omy in  taking  down,  carrying  and  re-erecting  forms  a  car- 
dinal point  should  be  that  the  work  be  such  that  it  can  be 
executed  by  common  laborers.  This  result  can  be  very  nearly 
approached  by  careful  design,  even  for  form  work  that  is  quite 
complex,  if  a  special  gang  is  devoted  to  the  work  and  trained 
a  little  in  the  various  operations.  Design  the  forms  so  that 
they  come  apart  in  units  by  simply  removing  bolts,  clamps 
and  wedges.  They  can  then  be  taken  down,  carried  and 
erected  by  common  laborers  with  a  skilled  man  in  charge  to 
meet  emergencies  and  to  true  and  line  up  the  work. 


FORM  CONSTRUCTION.  143 

In  the  matter  of  details  the  joints  deserve  particular  atten- 
tion. In  column  and  girder  forms,  generally,  joints  will  be 
square  or  butt  joints,  and  to  get  them  tight  the  lumber  must 
be  dressed  true  to  edge.  Tight  joints  are  considered  essential 
by  many  not  only  to  avoid  joint  marks  but  for  the  more 
important  reason  that  otherwise,  with  wet  mixtures,  a  honey- 
combed concrete  is  produced  by  leakage.  Where  tight  joints 
are  desired  tongue  and  groove  stock  or  stock  cut  with  one  edge 
beveled  and  the  other  square  give  the  best  results.  The 
authors  believe  that  the  best  general  satisfaction  will  be  got 
from  the  bevel  edge  stock  placed  so  that  the  bevel  edge  of  one 
board  comes  against  the  square  edge  of  the  next  board ;  undue 
swelling  then  results  in  the  bevel  edge  cutting  into  the  ad- 
jacent square  edge  without  bulging.  Tongues  and  grooves 
suffer  badly  from  breakage.  As  a  matter  of  fact  square  edged 
stock,  if  well  dressed  and  sized  and  well  filled  with  moisture, 
can  be  used  and  is  used  with  entire  success  in  nearly  all  kinds 
of  work.  The  leakage  will  be  very  slight  with  ordinarily  good 
butt  joints  and  so  far  as  surface  appearance  goes  joint  marks 
are  more  cheaply  and  more  satisfactorily  eliminated  by  other 
means  than  attempting  to  get  cabinet  work  in  form  construc- 
tion. Where  girder  forms  join  columns  or  beams  connect 
with  girders  and  at  the  angles  of  floor  slabs  with  beams  the 
edges  or  corners  of  the  forms  should  be  rounded.  The  edges 
of  beams  and  column  corners  will  appear  better  if  beveled ;  a 
triangular  strip  in  the  corners  of  the  forms  will  provide  this 
bevel.  Forms  and  mold  construction  for  ornamental  work  call 
for  and  are  given  special  consideration  in  Chapter  XXIII.  In 
conclusion,  the  reader  should  study  the  specific  examples  of 
form  construction  for  different  purposes  that  are  given 
throughout  the  book  for  hints  as  to  special  practice  and 
details. 

UNIT  CONSTRUCTION  OF  FORMS.— Unit  construc- 
tion has  a  somewhat  variable  meaning  in  form  work.  In  wall 
and  tank  work  and  in  some  other  kinds  of  work  unit  construc- 
tion means  the  use  of  form  units  which  are  gradually  moved 
ahead  or  upward  as  the  concreting  progresses  or  of  form  units 
which  are  used  one  after  another  in  continuous  succession  as 
the  concreting  progresses.  In  column,  girder  and  floor  work 
unit  construction  means  the  division  of  the  form  work  as  a 


144 


CONCRETE    CONSTRUCTION. 


whole  and  also  of  the  individual  forms  into  independent  struc- 
tural units ;  thus  in  forms  for  a  building  the  column  forms 
may  be  independent  of  the  girder  forms  and  also  each  column 
and  girder  form  be  made  up  of  several  separate  units.  In  all 
cases  unit  construction  has  for  its  purpose  the  use  of  the  same 
form  or  at  least  the  same  form  lumber  over  and  over  for  mold- 
ing purposes.  Every  time  the  use  of  the  same  form  is  re- 
peated, the  cost  of  form  work  per  cubic  yard  of  concrete  placed 
is  reduced.  The  theoretical  limit  of  economical  repetition  is 
then  the  limit  of  endurance  of  the  form,  the  practical  limit, 
however,  is  something  quite  different.  Most  concrete  work 
varies  in  form  'or  dimensions  often  enough  to  prevent  the  use 
of  the  same  forms  more  than  a  few  times,  and  even  if  these 
variations  did  not  exist  the  time  element  would  enter  to  pre- 
vent the  same  form  or  form  lumber  being  used  more  than  a 
certain  number  of  times.  Unit  construction  to  give  repeated 
use  of  forming  has,  therefore,  its  economic  limits.  The  sig- 
nificance of  this  conclusion  does  not  lie  in  any  novelty  that  it 
possesses  but  in  the  fact  that  for  any  piece  of  work  it  deter- 
mines the  labor  that  may  profitably  be  expended  in  working 
out  and  constructing  form  units. 

LUBRICATION  OF  FORMS.— All  forms  for  concrete  re- 
quire a  coating  of  some  lubricant  to  prevent  the  concrete  from 
adhering  to  the  wood  with  which  it  comes  in  contact.  Inci- 
dentally this  coating  tends  to  give  a  smoother  surface  to  the 
concrete  and  to  preserve  the  wood  against  damage  by  its 
alternate  wetting  and  drying.  The  great  value  of  lubrication 
is,  however,  that  it  reduces  the  cost  of  removing  forms.  The 
requisite  of  a  good  coating  material  is  that  it  shall  be  thin 
enough  to  spread  evenly  and  to  fill  the  pores  and  grain  of  the 
wood.  Crude  oil  or  petroline  makes  one  of  the  best  coatings, 
but  various  other  greasy  substances  will  serve.  Where  the 
forms  are  not  to  be  removed  until  the  concrete  has  set  hard  a 
thorough  wetting  of  the  wood  just  before  the  concrete  is 
placed  is  all  the  coating  necessary.  Any  concrete  adhering  to 
forms  should  be  thoroughly  cleaned  off  before  they  are  used 
again  and  the  wood  underneath  given  a  special  heavy  coating. 

FALSEWORKS  AND  BRACING.— The  falseworks  which 
support  the  forms  proper  and  stagings  for  workmen,  runways, 
material  hoists,  etc.,  do  not  call  for  any  striking  differences  in 


FORM   CONSTRUCTION.  145 

construction  and  arrangement  from  such  work  elsewhere.  For 
wall  forms  inclined  props  reaching  from  ground  to  studding 
are  used  for  walls  of  moderate  height  such  as  retaining  walls, 
wing  walls,  and.  abutments.  For  building  walls  of  some 
height  a  gallows  frame  arrangement  or  the  corrrmon  braced 
staging  used  by  masons  and  carpenters  is  used.  In  building 
construction,  however,  movable  forms  are  commonly  em- 
ployed for  walls  more  than  one  stojy  high  and  should  always 
be  employed  above  one  story  to  save  staging  timber.  Column 
forms  are  seldom  braced  unless  erected  without  connecting 
girder  or  floor  forms  at  their  tops,  and  then  only  by  diagonal 
props  to  the  floor  or  ground.  Girder  and  floor  supports  usu- 
ally consist  of  uprights  set  under  the  girder  form  at  intervals 
and  occasionally  under  floor  slab  forms.  The  spacing  of 
props  and  uprights  will  be  regulated  by  the  judgment  of  the 
foreman  and  boss  carpenter;  no  general  rule  is  applicable, 
except  that  enough  lumber  must  be  used  to  hold  the  forms 
rigid  and  true  to  line  and  level.  The  various  illustrations  of 
actual  formwork  which  follow  are  the  best  guides  to  good 
practice. 

TIME  FOR  AND  METHOD  OF  REMOVING  FORMS. 
— No  exact  time  schedule  for  removing  forms  is  wise  in  con- 
crete work.  Concrete  which  is  mixed  wet  sets  slower  than 
dry  concrete  and  concrete  sets  slower  in  cold  weather  than  it 
does  in  warm  weather.  Again  the  time  of  removal  is  influenced 
by  the  risk  taken  by  too  early  removal,  and  also  by  the  nature 
of  the  stresses  in  the  member  to  be  relieved  of  support.  In  all 
cases  the  forms  should  be  removed  as  soon  as  possible  so  that 
they  can  be  used  over  again  and  so  that  the  concrete  may  be 
exposed  to  the  air  to  hasten  hardening:  The  following  sug- 
gestions as  to  time  of  removal  are  general  and  must  be  fol- 
lowed with  judgment. 

Using  dry  concrete  in  warm  weather  the  forms  for  retaining 
walls,  pedestals,  isolated  pillars,  etc.,  can  De  removed  in  12 
hours ;  using  wet  or  sloppy  concrete  the  time  will  be  increased 
to  24  hours.  In  cold  weather  the  setting  is  further  delayed 
and  inspection  is  the  only  safe  guide  to  follow.  Very  cold 
weather  delays  setting  indefinitely.  Forms  for  small  arch 
work  like  sewers  and  culverts  may  be  removed  in  18  to  24 
hours  if  dry  concrete  is  used,  and  in  24  to  48  hours  if  wet  con- 


146  CONCRETE    CONSTRUCTION. 

crete  is  used.  The  time  for  removing  large  arch  centers  should 
not  be  less  than  14  days  for  spans  up  to  50  ft.  if  the  arch  is 
backfilled  at  once ;  when  the  center  is  not  to  be  used  again  it 
is  better  to  let  it  stand  28  days.  For  very  large  arches  the 
problem  becomes  a  special  one  and  is  considered  in  Chapter 
XVII.  In  building  construction  the  following  schedule  is  a 
common  one.  Remove  the  column  forms  in  7  days  and  the 
sides  of  the  girder  forms  and  the  floor  lagging  in  14  days  leav- 
ing the  bottom  boards  of  the  girder  forms  and  their  supports 
in  place  for  21  days. 

As  an  example  of  individual  practice  the  following  require- 
ments of  a  large  firm  of  concrete  contractors  are  given : 

Walls  in  mass  work,  i  to  3  days,  or  until  the  concrete  will 
bear  pressure  of  the  thumb  without  indentation. 

Thin  walls,  in  summer,  2  days ;  in  cold  weather,  5  days. 

Slabs  up  to  6-ft.  span,  in  summer,  6  days ;  in  cold  weather, 
2  weeks. 

Beams  and  girders  and  long  span  slabs,  in  summer,  10  days 
or  2  weeks ;  in  cold  weather,  3  weeks  to  I  month.  If  shores 
are  left  without  disturbing  them,  the  time  of  removal  of  the 
sheeting  in  summer  may  be  reduced  to  I  week. 

Column  forms,  in  summer,  2  days ;  in  cold  weather,  4  days, 
provided  girders  are  shored  to  prevent  appreciable  weight 
reaching  columns. 

Conduits,  2  or  3  days,  provided  there  is  not  a  heavy  fill 
upon  them. 

Arches,  of  small  size,  i  week ;  for  large  arches  with  heavy 
dead  load,  i  month. 

The  method  of  removing  forms  will  vary  in  detail  with  the 
character  of  the  structure.  With  proper  design  and  lubrica- 
tion of  forms  they  will  ordinarily  come  away  from  the  concrete 
with  a  moderate  amount  of  sledge  and  bar  work.  If  the  work 
will  warrant  it,  have  a  special  gang  under  a  competent  fore- 
man for  removing  forms.  The  organization  of  this  gang  and 
the  procedure  it  should  follow  will  vary  with  the  nature  of 
the  form  work,  and  they  are  considered  in  succeeding  chapters 
for  each  kind  of  work. 

ESTIMATING  AND  COST  OF  FORM  WORK.— It  is 
common  practice  to  record  the  cost  of  forms  in  cents  per  cubic 
yard  of  concrete,  giving  separately  the  cost  of  lumber  and 


FORM    CONSTRUCTION.  l^j 

labor.  This  should  be  done,  but  the  process  of  analysis  should 
be  carried  further.  The  records  should  be  so  kept  as  to  show 
the  first  cost  per  1,000  ft.  B.  M.  of  lumber,  the  number  of  times 
the  lumber  is  used,  the  labor  cost  of  framing,  the  labor  cost  of 
erecting  and  the  labor  cost  of  taking  down,  all  expressed  in 
M.  ft.  B.  M.  In  this  way  only  is  it  possible  to  compare  the 
cost  of  forms  on  different  kinds  of  concrete  work,  and  thus 
only  can  accurate  predictions  be  made  of  the  cost  of  forms  for 
concrete  work  having  dimensions  differing  from  work  pre- 
viously done.  It  is  well,  also,  to  make  a  note  of  the  number 
of  square  feet  of  exposed  concrete  surface  to  which  the  forms 
are  applied. 

Some  of  the  items  mentioned  demand  brief  explanation. 
Framing  and  erecting  costs  are  kept  separate  for  the  reason 
that  the  framing  is  done  only  once,  whereas  the  erecting 
occurs  two  or  more  times.  The  lumber  cost,  where  the  ma- 
terial is  used  more  than  once,  can  be  computed  in  two  ways. 
An  example  will  illustrate  the  two  modes  of  procedure.  In 
one  of  the  buildings  described  in  Chapter  XIX  the  lumber  cost 
$30  per  M.  ft.  B.  M.  and  was  used  three  times.  As  34,000  ft. 
B.  M.  were  required  to  encase  the  200  cu.  yds.  of  concrete  in 
one  floor,  including  columns,  it  would  have  required  34,000  -f- 
200  —  170  ft.  B.  M.  of  lumber  at  $30  per  M.  per  cubic  yard  of 
concrete  if  it  had  been  used  only  once.  But  since  it  was  used 
three  times  we  may  call  it  170  ft.  B.  M.  at  $10  per  M.  per  cubic 
yard  of  concrete,  or  we  may  call  it  170-^-3  =  57  ft.  B.  M.  at 
$30  per  M.  per  cubic  yard  of  concrete.  The  authors  prefer  the 
first  method,  due  to  the  fact  that  it  is  170  ft.  B.  M.  that  is 
handled  and  taken  down  each  time  and  it  is  more  consistent  to 
have  the  lumber  cost  on  the  same  basis  thus : 

170  ft.  B.  M.  of  lumber  at  $10  per  M $1.70 

170  ft.  B.  M.  handled  at  $2  per  M 0.34 

170  ft.  B.  M.  erected  at  $7  per  M 1.19 


Total  170  ft.  B.  M.  per  cu.  yd $3.23 

Returning  to  our  main  thought,  there  are  three  ways  of 
recording  the  cost  of  form  work:  (i)  In  cents  per  cubic  yard 
of  concrete ;  (2)  in  cents  per  square  foot  of  concrete  face  to 
which  forms  are  applied,  and  (3)  in  dollars  per  1,000  ft.  B.  M. 
of  lumber  used.  In  all  cases  the  cost  of  materials  and  of  labor 


I48  CONCRETE    CONSTRUCTION. 

should  be  kept  separate.  It  is  well  if  it  can  be  done  to  attach 
a  sketch  of  the  forms  to  the  record.  So  much  for  the  general 
method  of  recording  costs  in  form  work. 

In  estimating  the  probable  cost  of  forms  for  any  job  the  fol- 
lowing method  will  be  found  reliable :  Having  the  total  cubic 
yards  of  concrete  in  the  work  and  the  time  limit  within  which 
the  work  must  be  completed  determine  the  number  of  cubic 
yards  that  must  be  placed  per  day,  making  liberal  allowances 
for  delays.  Next  estimate  the  number  of  thousands  of  feet 
board  measure  of  forms  required  to  encase  the  concrete  to  be 
placed  in  a  day.  This  will  give  the  minimum  amount  of  lum- 
ber required,  for  it  is  seldom  permissible  to  remove  the  forms 
until  the  concrete  has  hardened  over  night.  Now  we  come  to 
the  very  important  and  puzzling  question  of  the  time  element, 
particularly  in  work  where  it  is  possible  to  use  the  same  forms 
or  the  same  form  lumber  two  or  more  times. 

It  has  already  been  pointed  out  that  wet  concrete  sets  more 
slowly  than  dry  concrete ;  that  all  concrete  sets  more  slowly 
in  cold  than  in  warm  weather,  and  that  the  support  of  forms 
is  necessary  a  longer  time  for  pieces  subject  to  bending  stress 
like  arches  and  girders.  General  suggestions  as  to  specific 
times  for  removing  forms  have  also  been  given.  Where  the 
specifications  state  the  time  of  removal  the  contractor  has  a 
definite  guide,  but  where  they  do  not,  as  is  most  often  the  case, 
he  must  depend  very  largely  on  judgment  and  previous  ex- 
perience. Another  matter  which  deserves  consideration  is  ..he 
use  of  the  forms  as  staging  for  runways  or  tracks.  Such  Uoe 
may  result  in  forms  having  to  stand  on  work  for  sake  of  their 
service  as  trestles  much  longer  than  there  is  any  necessity  so 
far  as  supporting  the  concrete  is  concerned.  A  derrick  or 
cableway  may  often  prove  cheaper  than  tieing  up  form  lumber 
by  trying  to  make  it  serve  the  double  purpose  of  a  trestle. 

The  possibilities  of  repeated  use  of  forms  and  of  unit  con- 
struction of  forms  have  already  been  noted.  This  is  the  next 
point  to  be  considered  in  estimating  form  lumber.  At  the 
expense  of  a  little  planning  movable  forms  can  be  used  to 
materially  reduce  the  amount  of  lumber  required.  The  reader 
is  referred  particularly  to  the  chapters  on  retaining  wall,  con- 
duit and  building  work  for  specific  data  on  movable  form 
\vork. 


FORM   CONSTRUCTION. 


149 


Having  estimated  the  amount  of  lumber  required  and  the 
number  of  times  it  can  be  used  the  labor  cost  of  framing, 
erecting  and  taking  down  can  be  figured.  In  ordinary  retain- 
ing wall  work  forms  will  cost  for  framing  and  erection  from 
$6  to  $7  per  M.  ft.  B.  M.  To  tear  down  such  forms 
carefully  and  to  carry  the  lumber  a  short  distance  will  cost 
some  $1.50  to  $2  per  M.  ft.  B.  M.  We  have  then  a 
cost  of  $7.50  to  $9  per  M.  ft.  B.  M.  for  each  time  the 
forms  are  erected  and  torn  down.  Where  movable  panels  are 
used  and  the  forms  not  ripped  apart  and  put  together  again 
each  time  there  is  of  course  only  the  cost  of  moving,  which 
may  run  as  low  as  50  cts.  per  M.  ft.  B.  M.  Framing  and  erect- 
ing centers  for  piers  will  run  about  the  same  as  for  retaining 
wall.  At  this  point  it  may  be  noted  that  in  estimating  the  cost 
of  forms  for  plain  rectangular  piers  the  following  method  will 
give  very  accurate  results.  Ascertain  the  surface  area  of  the 
four  sides  of  the  pier.  Multiply  this  area  by  2,  and  the  prod- 
uct will  be  the  number  of  feet  board  measure  of  2-in.  plank 
required.  Add  40  per  cent,  to  this,  and  the  total  will  be  the 
number  of  feet  board  measure  of  2-in.  plank  and  of  upright 
studs  (4x6),  spaced  2^2  ft.  centers.  Sometimes  3  x  6-in.  studs 
are  used,  and  spaced  2  ft.  centers,  which  requires  practically 
the  same  percentage  (40  per  cent.)  of  timber  for  the  studs  as 
where  4  x  6-in.  studs  are  used  and  spaced  2^/2  ft.  centers.  No 
allowance  is  made  for  timber  to  brace  the  studs,  since,  in  pier 
work,  it  is  customary  to  hold  the  forms  together  either  with 
bolts  or  with  ordinary  No.  9  telegraph  wire,  which  weighs 
0.06  Ib.  per  foot.  The  foregoing  data  can  be  condensed  into 
a  rule  that  is  easily  remembered : 

Multiply  the  number  of  square  feet  surface  area  of  the  sides 
and  ends  of  a  concrete  pier  by  2.8,  and  the  product  will  be  the 
number  of  feet  board  measure  required  for  sheet  plank  and  studs 
for  the  forms. 

If  the  form  lumber  can  be  used  more  than  once,  divide  the 
number  of  feet  board  measure  by  the  number  of  times  that  it 
can  be  used,  to  ascertain  the  amount  to  be  charged  to  each 
pier.  Forms  can  be  erected  and  taken  down  for  $8  per  M. 
carpenters  being  paid  $2.50  and  laborers  $1.50  a  day. 
Since  there  are  2.8  ft.  B.  M.  of  forms  per  square  foot  of  surface 
area  of  concrete  to  be  sheeted,  it  costs  2l/±  cts.  for  the  labor  of 


I5o  CONCRETE    CONSTRUCTION. 

carpenters  per  square  foot  of  surface  area  to  be  sheeted.  If 
lumber  is  worth  $24  per  M.,  and  is  used  three  times,  then  the 
lumber  itself  also  costs  2T4  cts.  per  sq.  ft.  of  surface  area  of 
concrete.  By  dividing  the  total  number  of  cubic  yards  of  con- 
crete into  the  total  number  of  square  feet  of  area  of  surface  to 
be  sheeted  with  forms,  the  area  per  cubic  yard  is  obtained. 
Multiply  this  area  by  4^/2  cts.,  and  the  product  is  the  cost  per 
cubic  yard  for  material  in  the  forms  (assumed  to  be  used  three 
times)  and  the  labor  of  erecting  it  and  taking  it  down. 

The  cost  of  framing  and  erection  of  forms  for  building  work 
and  of  centers  for  large  arches  is  a  special  problem  in  each 
case  and  is  considered  in  the  chapters  devoted  to  those  classes 
of  work. 


CHAPTER   X. 

METHODS    AND    COST    OF    CONCRETE    PILE   AND 
PIER  CONSTRUCTION  FOR  FOUNDATIONS. 

Two  general  methods  of  concrete  pile  construction  are 
available  for  engineering  work.  By  one  method  a  hole  is 
formed  in  the  ground  by  driving  a  steel  shell  or  by  other 
special  means  and  this  hole  is  filled  with  concrete.  By  the 
other  method  the  pile  is  molded  in  suitable  forms  and  after 
becoming  hard  is  driven  as  a  wood  or  steel  pile  is  driven. 
Piles  constructed  by  the  first  method  may  be  either  plain  or 
reinforced,  but  piles  constructed  by  the  second  method  are 
always  reinforced  to  strengthen  them  for  handling  and  driv- 
ing. Concrete  piers  for  foundation  work  are  simply  piles  of 
enlarged  diameter. 

MOLDING  PILES  IN  PLACE.— Molding  piles  in  place 
requires  the  use  of  special  apparatus,  and  this  apparatus  is  to 
a  very  large  degree  controlled  by  patents.  Pile  work  of  this 
kind  is  thus  generally  done  by  concerns  which  control  the  use 
of  the  apparatus  employed  and  the  general  contractor  can 
undertake  it  only  by  permission  of  the  proprietary  companies. 
The  methods  of  work  followed  and  the  cost  of  work  are  thus 
of  direct  interest  only  as  general  information. 

Method  and  Cost  of  Constructing  Raymond  Piles. — The  ma- 
chinery and  processes  employed  in  the  construction  of  Ray- 
mond concrete  piles  are  patented  and  all  piling  work  by  this 
method  is  controlled  by  the  Raymond  Concrete  Pile  Co.  As 
detail  costs  of  construction  are  not  given  out  by  the  company 
the  following  figures  collected  by  the  authors  are  subject  to 
revision.  They  are  believed  to  be  fairly  approximate,  having 
in  one  case  been  obtained  by  personal  watch  on  the  work  and 
in  the  other  case  from  authentic  records  of  the  engineers  on 
the  work. 

The  pile  is  made  as  follows  •/  A  collapsible  steel  core  30  ft. 
long,  20  ins.  diameter  at  the  top  and  6  ins.  diameter  at  the 


152 


CONCRETE    CONSTRUCTION. 


bottom,  encased  in  a  thin  sheet  steel  shell,  is  driven  into  the 
ground  by  an  ordinary  pile  driver.  When  it  has  reached  the 
proper  depth,  a  wedge  is  loosened,  permitting  the  two  sections 
of  the  core  to  come  closer  together  so  that  the  core  can  be 
pulled  out  of  the  hole,  leaving  the  steel  shell  behind  as  a 
casing  to  prevent  the  sides  from  caving  in.  The  shell  is  made 
of  No.  20  gage  steel,  usually  in  four  or  more  sections,  which 
telescope  one  over  the  other.  A  nest  of  sections  is  slipped 
over  the  lower  end  of  the  core  as  it  hangs  in  the  leads,  a  rope 
is  hitched  around  the  outer  section  and  the  engine  hoists  away 
until  the  sections  are  "un-telescoped"  and  drawn  snug  onto 
the  core.  The  rope  is  then  unfastened  and  the  driving  begins. 
Figure  49  shows  the  usual  pile  driving  rig  used.  The  follow- 
ing are  examples  of  pile  construction  in  actual  work : 

Example  I. — In  this  work,  for  a  building  foundation  in  New 
York  City,  the  pile  driver  was  mounted  on  a  turntable,  the 
framework  of  the  turntable  in  turn  resting  on  rollers  traveling 
on  timbers  laid  on  the  ground.  The  driver  was  moved  along 
and  rotated  when  necessary  by  ropes  passing  around  the 
winch  head  of  the  engine.  The  driver  had  5O-ft.  leads 
and  a  3,ioo-lb.  hammer  operated  by  an  ordinary  friction  clutch 
hoisting  engine.  The  hammer  blow  was  received  by  an  oak 
block  fitting  into  a  recess  at  the  top  of  the  steel  core.  This 
block  was  so  battered  by  the  blows  that  it  had  to  be  renewed 
about  every  five  or  six  piles  driven.  A  ^-in.  wire  rope  passing 
over  a  lo-in.  sheave  lasted  for  the  driving  of  130  piles  and 
then  broke.  When  the  work  was  first  begun  the  crew  aver- 
aged 10  piles  per  lo-hour  day,  but  the  average  for  the  job  was 
13  piles  per  day,  and  the  best  day's  work  was  17  piles.  The 
cost  of  labor  and  fuel  per  pile  was  as  follows : 

5  men  on  driver  at  $1.75 $  8.75 

2  men  handling  shells  at  $1.75 3.50 

i  engineman 3.00 

6  men  mixing  and  placing  concrete. 10.50 

I  foreman  5.00 

Coal  and  oil   2.50 

Total,  13  piles,  at  $2.55 $33.25 

Deducting    the    cost    of    placing   the    concrete    we    get    a 
cost    of    $1.75    for    driving    the    cores.       The    pile,    25    ft. 


CONCRETE    PILE    FOUNDATIONS. 


153 


Fig. 


49._pnP  Driver  Rigged  for  Constructing 
Raymond   Concrete   Piles. 


long,  6  ins.  at  the  point  and  18  ins.  at  the  head,  contains  2il/4 
cu.  ft.,  or  0.8  cu.  yd.,  of  concrete,  and  has  a  surface  area  of 
77  ft.  As  No.  20  steel  weighs  1.3  Ibs.  per  sq.  ft.,  each  shell 


154  CONCRETE    CONSTRUCTION, 

weighed  approximately  100  Ibs.     The  cost  per  pile  may  then 

be  summarized  as  follows : 

1.2  bbls.  cement  in  0.8  cu.  yd.,  at  $1.75 $2.10 

0.8  cu.  yd.  stone  at  $1.25  i.oo 

1-3  cu.  yd.,  sand  at  $1.05 0.35 

100  Ibs.  steel  in  shell  at  3^2  cts 3.50 

Labor  and  fuel  as  above 2.55 

Total  per  pile   (38  cts.  per  lin.  ft.) $9-5° 

This  cost,  it  should  be  carefully  noted,  does  not  include  cost 
of  moiing  plant  to  and  from  work  or  general  expenses. 

Example  II. — In  constructing  a  building  at  Salem,  Mass., 
172  foundation  piles,  14  to  37  ft.  long,  6  ins.  diameter  at  the 
point  and  20  ins.  diameter  at  the  top,  were  constructed  by  the 
Raymond  process.  The  general  contractor  made  the  neces- 
sary excavations  and  provided  clear  and  level  space  for  the 
pile  driver,  braced  all  trenches  and  pier  holes,  set  stakes  for 
the  piles  and  gave  all  lines  and  levels.  The  piles  were  driven 
by  a  No.  2  Vulcan  steam  hammer  with  a  3,ooo-lb.  plunger  hav- 
ing a  drop  of  3  ft.,  delivering  60  blows  per  minute.  Figure  49 
shows  the  driver  at  work.  Sixteen  working  days  were  occu- 
pied in  driving  the  piles  after  the  driver  was  in  position.  The 
greatest  number  driven  in  one  day  was  20,  and  the  average  was 
ii  piles  per  day.  When  in  position  for  driving,  the  average 
time  required  to  complete  driving  was  12  minutes.  The  total 
number  of  blows  varied  from  about  310  to  360,  the  average 
being  about  350.  The  piles  were  driven  until  the  penetration 
produced  by  8  to  10  blows  equaled  I  in.  When  in  full  opera- 
tion, a  crew  of  5  men  operated  the  pile  driver.  Seven  men 
were  engaged  in  making  the  concrete  and  5  men  working  upon 
the  metal  shells. 

Assuming  the  ordinary  organization  and  the  wages  given 
below,  we  have  the  following  labor  cost  per  day: 

i  foreman  at  $5  $  5-°° 

I  engineman  at  $3 3-°° 

4  laborers  on  driver  at  $1.75 7-°° 

6  laborers  making  concrete  at  $1.75 10.50 

5  laborers  handling  shells  at  $1.75  8.75 

Total  $34-25 


CONCRETE    PILE    FOUNDATIONS. 


155 


As  172  piles  averaging  20  ft.  in  length  were  driven  in  16 
days,  the  total  labor  cost  of  driving,  given  by  the  figures 
above,  is  16  X  $34.25  =  $548,  or  practically  16  cts.  per  lineal 
foot  of  pile  driven. 

The  concrete  used  in  the  piles  was  a  1-3-5  Portland  cement, 
sand  and  il/2-m.  broken  stone  mixture.  A  2O-ft.  pi^e  of  the 
section  described  above  contains  about  20  cu.  ft.  of  concrete, 
or  say  0.75  cu.  yd.  We  can  then  figure  the  cost  of  concrete 
materials  per  pile  as  follows : 

0.85  bbl.  cement  at  $1.60 $1.36 

0.36  cu.  yd.  sand  at  $i .   0.36 

0.60  cu.  yd.  stone  at  $1.25  0.75 

*  Total  per  pile   $2.47 

The  steel  shell  has  an  area  of  about  72  sq.  ft.,  and  as  No. 
20  gage  steel  weighs  1.3  Ibs.  per  sq.  ft.,  its  weight  for  each 
pile  was  about  94  Ibs.  Assuming  the  cost  of  coal,  oil,  etc.,  at 
$2.50  per  day,  we  have  the  following  summary  of  costs : 

Perlin.ft. 
of  pile. 

Labor  driving  and  concreting $0.16 

Concrete  materials 0.123 

94  Ibs.  steel  shell  at  3  cts 0.145 

Coal,  oil,  etc o.oi  I 


Total  $0.439 

The  cost  does  not  include  interest  on  plant,  cost  of  moving 
plant  to  and  from  ivork  and  general  expenses. 

Method  of  Constructing  Simplex  Piles. — The  apparatus  em- 
ployed in  driving  Simplex  piles  resembles  closely  the  ordinary 
wooden  pile  driven,  but  it  is  much  heavier  and  is  equipped  to 
pull  as  well  as  to  drive.  A  3,300-!!).  hammer  is  used  and  it 
strikes  on  a  hickory  block  set  in  a  steel  drive  head  which  rests 
on  the  driving  form  or  shell.  This  form  consists  of  a  ^-in. 
steel  shell  16  ins.  in  diameter  made  in  a  single  4O-ft.  length. 
Around  the  top  of  the  shell  a  j^-in.  thick  collar  or  band  18  ins. 
deep  is  riveted  by  24  i-in.  countersunk  rivets.  This  band 
serves  the  double  purpose  of  preventing  the  shell  being  upset 
by  the  blows  of  the  hammer  and  of  giving  a  grip  for  fastening 
the  pulling  tackle.  The  bottom  of  the  form  or  shell  is  pro- 


156 


COXCRLTK    COXSTRI'CTIOX. 


vided  with  a  point.  Two  styles  of  point  are  employed.  One 
style  consists  of  two  segments  of  a  cylinder  of  the  same  size 
as  the  form,  so  cut  that  they  close  together  to  form  a  sort  of 
clam  shell  point.  In  driving,  the  two  jaws  are  held  closed  by 
the  pressure  of  the  earth  and  in  pulling  they  open  apart  of 
their  own  weight  to  permit  the  concrete  to  pass  them.  This 
point,  known  as  the  alligator  point;  is  pulled  with  the  shell.  It 
is  suitable  only  for  driving  in  firm,  compact  soil,  in  loose  soil 
the  pressure  inward  of  the  walls  keeps  the  jaws  partly  closed 
and  so  contracts  the  diameter  of  the  finished  pile.  The  second 
style  of  point  is  a  hollow  cast  iron  point,  10  ins.  deep  and 


Fig.    SO.— Sketch    Showing   Method    of   Constructing   Simplex    Concrete    Piles. 

i6j/2  ins.  in  diameter,  having  a  neck  over  which  the  driving 
form  slips  and  an  annular  shoulder  outside  the  neck  to  receive 
the  circular  edge  of  the  shell.  The  projected  sectional  area  of 
this  point  is  1.4  sq.  ft.  It  is  left  in  the  ground  when  the  form 
is  withdrawn.  The  form  is  withdrawn  by  means  of  two  i-in. 
cables  fastened  to  a  steel  collar  which  engages  under  the  band 
at  the  top  of  the  form.  The  cables  pass  in  the  channel  leads 
on  each  side  over  the  head  of  the  driver  and  down  in  back  to  a 
pair  of  fivefold  steel  blocks,  the  lead  line  from  which  passes 
to  one  of  the  drums  of  the  engine.  In  this  manner  the  power 
of  the  drum  is  increased  ten  times  and  it  is  not  unusual  to 


CONCRETE    PILE    FOUNDATIONS. 


157 


break  the  pulling  cables  when  the  forms  are  in  hard  ground. 
The  general  method  of  construction  is  about  as  shown  by  Fig. 
50,  being  changed  slightly  to  meet  varying  conditions.  The 
form  resting  on  a  cast  iron  point  is  driven  to  hard  ground.  A 
heavy  weight  is  then  lowered  into  the  form  to  make  sure  the 
point  is  loose.  While  the  weight  is  at  the  bottom  of  the  form 
a  target  is  placed  on  its  line  at  the  top  of  the  form,  the  pur- 
pose of  which  will  be  apparent  later.  The  weight  is  then 
withdrawn.  Given  the  length  of  the  pile  and  sectional 
area,  it  is  an  easy  matter  to  determine  the  volume  of  concrete 
necessary  to  fill  the  hole. 

This  amount  is  put  into  the  form" by  means  of  a  specially 
designed  bottom  dump  bucket,  which  permits  the  concrete  to 
leave  it  in  one  mass,  reaching  its  destination  with  practically 
no  disintegration.  It  will  be  noticed  that  when  the  full 
amount  of  concrete  is  in  the  form  its  surface  is  considerably 
above  the  surface  of  the  ground.  This  is  due  to  the  fact  that 
the  thickness  of  the  form  occupies  considerable  space  that  is 
to  be  occupied  by  the  concrete.  The  weight  is  now  placed 
on  top  of  the  concrete  and  the  form  is  pulled.  The  target 
previously  mentioned  now  becomes  useful.  As  the  form  is 
withdrawn  the  concrete  settles  down  to  occupy  the  space  left 
by  the  walls  of  the  form.  Obviously  this  settlement  should 
proceed  at  a  uniform  rate,  and  as  it  is  difficult  to  watch  the 
weight,  the  target  on  its  line  further  up  is  of  considerable 
help.  By  watching  this  target  in  connection  with  a  scale  on 
the  leads  of  the  driver,  it  can  be  readily  told  how  the  concrete 
in  the  form  is  acting.  As  another  check,  the  target,  just  as 
the  bottom  of  the  form  is  leaving  the  ground  should  be  level 
with  the  top  of  the  form.  This  would  indicate  that  the  neces- 
sary amount  of  concrete  has-  gone  into  the  ground  and  that, 
other  conditions  being  all  right,  the  pile  is  a  good  one.  In 
some  grounds  where  the  head  of  concrete  in  the  form  exerts 
a  greater  pressure  than  the  back  pressure  or  resistance  of  the 
earth,  the  Concrete  will  be  forced  out  into  the  sides  of  the  hole, 
making  the  pile  of  increased  diameter  at  that  point  and  neces- 
sitating the  use  of  more  concrete  to  bring  the  pile  up  to  the 
required  level. 

Method  of  Constructing  Piles  with  Enlarged  Footings.-— A 
pile  with  an  enlarged  base  or  footing  has  been  used  in  several 


158 


CONCRETE    CONSTRUCTION. 


places  by  Mr.  Charles  R.  Gow  of  Boston,  Mass.,  who  has 
patented  the  construction.  A  single  pipe  or  a  succession  of 
pipes  connected  as  the  work  proceeds  is  driven  by  hammer  to 
the  depths  required.  The  material  inside  the  shell  is  then 
washed  out  by  a  water  jet  to  the  bottom  of  the  shell  and  then 
for  a  further  distance  below  the  shell  bottom.  An  expanding 
cutter  is  then  lowered  to  the  bottom  of  the  hole  and  rotated 
horizontally  so  as  to  excavate  a  conical  chamber,  the  water 
jet  washing  the  earth  out  as  fast  as  it  is  cut  away:  When  the 
chamber  has  been  excavated  the  water  is  pumped  out  and  the 
chamber  and  shell  are  filled  with  concrete.  The  drawings  of 
Fig.  51  show  the  method  of  construction  clearly.  The  cham- 


-*i  8 


** 


Surface 


8"« 


of    Grounef 


'8ffWJ.piPe  —•+ 


V& 


8 


..-.  f 


Chamber  jnq 

%:         // *  -:'. *- . ".^          Machine. 
V        47. 1,.- '^ ••»'.*  :  'V. 


pe     i^TjTjFsg  ••  ^r-3,0/,'/-v 

Chamber  Excavatert. 


out. 

Fig.    51. — Sketch    Showing  Method   of   Constructing   Concrete    Piles   with 
Enlarged  Footings. 

bering  machine  is  used  only  in  clay  or  other  soil  which  does 
not  wash  readily.  In  soil  which  is  readily  washed  the  cham- 
ber can  be  formed  by  the  jet  alone.  The  practicability  of  this 
method  of  construction  is  stated  by  Mr.  Gow  to  be  limited  to 
pipe  sizes  up  to  about  14  ins.  in  diameter. 

Method  of  Constructing  Piles  by  the  "Compressor  System. 
—The  compressol  system  of  concrete  pile  or  pillar  construc- 
tion is  a  French  invention  that  has  been  widely  used  abroad 
and  which  is  controlled  in   this  country  by  the  Hennebique 
Construction   Co.,  of  New  York,  N.  Y.     The  piles  are  con- 


CONCRETE    PILE    FOUNDATIONS. 


159 


structed  by  first  ramming  a  hole  in  the  ground  by  repeatedly 
dropping  a  conical  "perforator"  weighing  some  two  tons. 
This  perforator  is  raised  and  dropped  by  a  machine  resem- 
bling an  ordinary  pile  driver.  The  conical  weight  gradually 
sinks  the  hole  deeper  and  deeper  by  compacting  the  earth 
laterally;  this  lateral  compression  is  depended  upon  so  to 
consolidate  the  walls  of  the  hole  that  they  do  not  cave  before 
the  concrete  can  be  placed.  The  concrete  is  deposited  loose  in 
the  hole  and  rammed  solid  by  dropping  a  pear-shaped  weight 
onto  it  as  it  is  placed.  The  view  Fig.  52  shows  the  "perforator" 


Fig.  52.— View  of  Apparatus  Used  in  Constructing  Compressol  Piles. 

and  the  tamping  apparatus  at  work.     Very  successful  work- 
has  been  done  abroad  by  this  method. 

Method  of  Constructing  Piers  in  Caissons. — For  piles  or  pil- 
lars of  diameters  larger  than  say  18  ins.  the  use  of  driving 
shells  and  cores  becomes  increasingly  impracticable.  Con- 
crete pillars  of  large  size  are  then  used.  They  are  constructed 
by  excavating  and  curbing  a  well  or  shaft  and  filling  it  with 
concrete.  This  construction  has  been  most  used  in  Chicago. 
111.,  for  the  foundations  for  heavy  buildings,  but  it  is  of  gen- 


i6o 


CONCRETE    CONSTRUCTION. 


eral  application  where  the  subsoil  conditions  are  "suitable. 
The  method  is  not  patented  or  controlled  by  patents  in  any 
particular,  except  that  certain  tools  and  devices  which  may  be 
used  are  proprietary. 

General  Description. — The  caisson 
method  of  construction  is  simple  in 
principle.  A  well  is  dug  by  successive 
excavations  of  about  5  ft.  each.  After 
each  excavation  of  5  ft.  is  completed, 
wood  lagging  is  placed  around  the 
sides  and  supported  by  internal  steel 
rings,  so  that  the  soft  ground  around 
the  excavation  is  maintained  in  its 
former  position.  Tl\e  methods  of  ex- 
cavating and  removing  the  soil  and  of 
constructing  the  lagging  are  consid- 
ered in  detail  further  on.  The  caissons 
vary  in  diameter  according  to  the  load ; 
some  as  large  as  12  ft.  in  diameter  have 
been  sunk,  but  the  usual  diameter  is  6 
ft. ;  a  caisson  of  3  ft.  in  diameter  is  as 
small  as  a  man  can  get  into  and  work. 
When  the  pier  goes  to  bed  rock  the 
caisson  is  made  of  uniform  diameter 
from  top  to  bottom,  but  where  the  pier 
rests  on  harapan  the  bottom  portion  of 
the  well  is  belled  out  to  give  greater 
bearing  area.  It  is  customary  to  load 
the  piers  about  20  tons  per  square  foot. 
Caisson  Construction. — The  caisson 
construction,  or  more  correctly  the 
form  of  curbing  most  commonly  used, 
is  that  indicated  by  the  sketch,  Fig. 
53.  The  lagging  is  2x6  in.  or  3x6 
in.,  stuff  5  ft.  4  ins.  or  4  ft.  long  set 
vertically  around  the  well  and  held  in 
place  by  interior  wrought  iron  rings, 
caisson  these  hoops  are  %  by  3  ins.;  they  are  made  in  two 
parts,  which  are  bolted  together  as  shown  by  Fig.  53.  Gen- 
erally there  are  two  rings  for  each  length  of  lagging;  for  5-ft. 


Fig.   53.— Curbing  for 

Concrete  Piers   (Usual 

Construction). 

For  a  6-ft.  diameter 


CONCRETE    PILE    FOUNDATIONS. 


161 


lagging  they  are  placed  about  9  ins.  from  each  end.  In  some 
cases,  however,  engineers  have  specified  three  rings  for  the 
upper  sections  in  soft  clay  and  two  rings  for  the  sections  in 
the  hard  ground  lower  down.  The  lagging  used  is  not  cut 
with  radial  edges,  but  is  rough,  square  cut  stuff;  the  rings, 
therefore,  take  the  inward  pressure  altogether. 

In   some  recent  work   done  by  the  inventor  use  has  been 
made  of  the  caisson  construction  shown  by  Fig.  54  and  pat- 


Fig.   54.— Curbing  for  Concrete  Piers   (Jackson  Patent). 

ented  by  Mr.  Geo.  W.  Jackson.  In  place  of  the  plain  rings  a 
combination  of  T-beam  ribs  and  jacks  is  used ;  this  construc- 
tion is  clearly  shown  by  the  drawing.  The  advantages  claimed 
for  the  construction  are  that  it  gives  absolute  security  to  the 
workmen  and  the  work,  that  the  lagging  can  be  jacked  tightly 
against  the  outer  walls  of  the  well,  that  the  braces  form  a 
ladder  by  which  the  workmen  can  enter  and  leave  the  well, 
and  that  the  possibility  of  shifting  the  bracing  easily  permits 
the  concrete  to  be  placed  to  the  best  advantage.  On  the 


162 


CONCRETE    CONSTRUCTION. 


£ 


q  o  o 

^'Caissons--' 

o  do  o.o  Q 


Portable  Ry. 


,'D/rf  Hoppers 

!  .'Platforms  orerCa/ssot 


9  °  °  p  c 

^Caissons 

OOO 


o 


other  hand  the  braces  abstruct  the  clear  working  space  of  the 
caissons. 

Excavating  and  Handling  Material. — The  excavation  of  the 
wells  is  done  by  hand,  using  shovels  and  picks,  and,  in  the 
hardpan,  special  grubs  made  by  A.  J.  Pement  and  George 
Racky,  Chicago  blacksmiths.  The  excavated  material  is 
hoisted  out  of  the  well  in 
buckets  made  by  the  Va- 
riety Iron  Works,  of  Chi- 
cago. For  caissons  which 
are  not  specified -to  go  to 
rock  it  is  considered  more 
economical  to  do  the 
hoisting  by  windlass  der- 
ricks operated  by  hand. 
These  derricks  have  four 
6x6-in.  legs  and  a  3x6- 
in.  top  piece.  When  the 
caissons  go  to  rock  the 
hoisting  is  done  by  power, 
so-called  "cable  set-ups" 
being  used  in  most  cases. 
To  illustrate  this  method 
the  following  account  of 
the  foundation  work  for 
the  Cook  County  Court 
House  is  given  : 

The  Cook  County  Court 
House  foundations  con- 
sist of  126  caissons  vary- 
ing from  4  ft.  to  10^  ft.  WW""**"**** 

.       j.  j  Transverse     Section, 

in     diameter    and    averag-  Fig.  55.— Layout  of  Plant  for  Concrete  Pier 
ing    7]/2     ft.     in      diameter.  Construction,  Cook  County  Court 

rp,,  House   Foundations. 

They  were  sunk  to  rock 

at  a  depth  of  115  ft.  below  street  level.  The  work  involved 
22,000  cu.  yds.  of  excavation  and  the  placing  in  the  caissons 
of  17,000  cu.  yds.  of  concrete.  Over  1,000  piles  about  40  ft. 
long,  that  had  formed  the  foundation  of  the  old  Court  House 
built  in  1875,  were  removed.  These  piles  were  found  to  be  in 
good  condition.  The  work  was  done  by  the  George  A.  Fuller 


#*> 


Randoph    St. 
Plan. 

A-A 


Caissons 


CONCRETE    PILE    FOUNDATIONS.  ^ 

Co.,  of  Chicago,  111.,  Contractors,  with  Mr.  Edgar  S.  Belden 
Superintendent  in  Charge.  The  details  which  follow  have 
been  obtained  from  Mr.  Belden. 

The  foundation  area  was  157x375  ft.,  and- was  excavated  to 
a  depth  of  15  ft.  below  the  street  surface  before  the  caissons 
were  started.  The  caissons,  of  which  there  were  126,  were 
arranged  in  rows  across  the  lot,  there  being  from  six  to  eight 
caissons  in  a  row.  The  arrangement  of  the  plant  for  the  work 
is  indicated  by  Fig.  55.  One  row  of  caissons  formed  a  unit.  A 


Fig.    56.— Section    Showing   Arrangement   of   Hoist    for    Concrete   Pier 
Construction. 

platform  or  "stand"  was  erected  over  each  caisson  and  carried 
in  its  top  a  tripod  fitted  with  a  "nigger  head"  operated  by  a 
rope  sheave.  This  arrangement  is  shown  by  Fig.  56.  An  .en- 
gine on  the  bank  operated  by  a  rope  drive  all  the  tripod 
sheaves  for  a  row  of  six  or  eight  caissons.  The  arrangement  is 
indicated  by  Fig.  55.  The  clay  hoisted  from  the  pits  was 
dumped  into  i  cu.  yd.  hoppers  with  which  the  stands  were 
fitted,  as  shown  by  Fig.  56;  when  a  hopper  was  full  it  was 
dumped  into  a  car  running  on  a  24-in.  gage  portable  track. 


1 64 


CONCRETE    CONSTRUCTION. 


Side    Eleva-Hon. 


End     Eleva-Hon. 


Side  dump  Koppel  cars  of 
i  cu.  yd.  capacity  were 
used ;  they  dumped  their 
load  into  an  opening  con- 
nected with  the  tracks  of 
the  Illinois  Tunnel  Co., 
where  the  material  passed 
into  tunnel  cars  and  was 
taken  to  the  lake  front 
about  one  mile  away.  As 
soon  as  one  row  of  cais- 
sons was  completed  the 
stands,  tripods,  etc., which 
were  made  portable,  were 
shifted  to  another  row. 
At  times  as  many  as  five 
units  were  in  operation, 
sinking  40  caissons. 

Fig.  56  shows  the  ar- 
rangement in  detail  at 
one  caisson.  In  this  work 
the  lagging  used  was  3  x  6-in.  maple,  5  ft.  4  ins.  long,  and 
was  .  supported  by  3  x  24-in.  steel  hoops.  The  lagging 
was  matched  and  dressed.  The  "nigger  head/'  as  will  be 


Bo-H-om       Plan, 


,'8x8 


i     2*6"     a 
Secfion. 


Fig.   57.— Details  of  Working  Platform 
for    Concrete    Pier    Construction. 


CONCRETE  PILE  FOUNDATIONS.         ^5 

seen,  is  operated  by  a  rope  sheave  on  the  same  axle.  As  stated 
above,  an  endless  rope  drive  operated  all  the  "nigger  heads" 
on  a  row  of  caissons.  A  26-in.  driving  sheave  was  attached  to 
an  ordinary  hoisting -engine  equipped  with  a  governor.  The 
driving  rope  was  ^6 -in.  steel.  It  was  wrapped  twice  around 
the  driving  sheave  and  once  around  the  "nigger  head*'  sheaves. 
These  latter  were  18  ins.  in  diameter.  For  the  hoists  i-in. 
Manila  rope  was  used.  The  other  details,  the  bucket,  bucket 
hook,  swivel  block,  etc.,  are  made  clear  by  the  drawing.  The 
platforms,  tripods,  etc.,  were  of  the  standard  dimensions  and 
construction  adopted  by  the  contractors  of  the  work.  Detail 
drawings  of  the  standard  platform  are  given  by  Fig.  57.  One 
of  these  platforms  contains  about  1,000  ft.  B.  M.  of  lumber. 
As  will  be  seen,  all  connections  are  bolted,  no  nails  being  used 
anywhere.  A  platform  can  thus  be  taken  down  and  stored  or 
shipped  and  erected  again  on  another  job  with  very  little 
trouble. 

The  plant  described  handled  some  22,000  cu.  yds.  of  exca- 
vated material  on  this  work.  Work  was  kept  up  night  and 
day,  working  three  8-hour  shifts.  It  took  an  average  of  35 
shifts  to  excavate  one  row  of  caissons.  No  figures  of  the 
working  force  or  the  cost  of  excavation  of  this  work  are 
available. 

Miring  and  Placing  Concrete. — The  placing  of  the  concrete 
in  the  excavated  wells  is  done  by  means  of  tremies,  or,  which 
is  more  usual,  by  simply  dumping  it  in  from  the  top,  workmen 
going  down  to  distribute  it.  The  manner  of  mixing  the  con- 
crete and  of  handling  it  to  the  caisson  varies  of  course  with 
almost  every  job.  As  an  example  of  the  better  arranged  mix- 
ing and  handling  plants  the  one  used  on  the  Cook  County 
Court  House  work  may  be  described.  This  plant  is  shown  by 
the  sketch,  Fig.  58. 

Bins  for  the  sand  and  stone  were  built  at  one  side  of  the  lot 
on  the  sloping  bank ;  their  tops  were  level  with  the  street  sur- 
face and  their  bottoms  were  just  high  enough  to  permit  their 
contents  to  be  delivered  by  chutes  into  i  cu.  yd.  cars.  Wagons 
dumping  through  traps  in  the  platform  over  the  bin  delivered 
the  sand  and  stone.  The  sketches  indicate  the  arrangement 
of  the  bins  and  mixer  and  the  car  tracks  connecting  them. 
The  raw  material  cars  were  first  run  under  the  stone  bin  and 


1 66 


CONCRETE    CONSTRUCTION. 


charged  with  the  required  proportion  of  stone,  and  then  to  the 
sand  bin,  where  the  required  proportion  of  sand  was  chutec! 
on  top  of  the  stone.  The  loaded  car  was  then  hauled  up  the 
incline  and  dumped  into  the  hopper,  where  cement  and  water 
were  added.  A  No.  2^/2  Smith  mixer  was  used  and  discharged 
into  cars  which  delivered  their  loads  on  tracks  leading  to  the 
caissons.  The  same  cars  and  portable  tracks  were  used  as  had 
been  used  to  handle  the  excavated  material.  In  operation  a 
batch  of  raw  materials  was  being  prepared  in  the  hopper  while 
the  previous  batch  was  being  mixed  and  while  the  concrete  car 
was  delivering  the  still  previous  batch  to  the  caissons.  An 
average  of  40  batches  an  hour  mixed  and  put  into  the  caissons 


Stone  and 
Sand  Wagons 


,-SteelSide         ifi^g 
y    Dump  Cars 


y//////////^v//^////^^ 
Section. 


By-Pass  -for  Empty  Cars 

Stee/ 
Hopper 

Z5H.R 
Electric 
Hoist 

1ST 

»*«* 

Platform 

Stone  Bin         Sand  Bin 


Plan. 


Fig.  58. — Arrangement  of  Concrete  Making  Plant,  Concrete  Pier  Construction 

was  maintained  with  a  force  of  25  men.  In  all  some  17,000  cu. 
yds.  of  concrete  were  mixed  and  deposited. 

Cost  of  Caisson  Work. — The  following  attempt  to  get  at  the 
cost  of  caisson  work  is  based  largely  upon  information  ob- 
tained from  Mr.  John  M.  Ewen,  John  M.  Ewen  Co.,  Engineers 
and  Builders,  Chicago,  111.  Mr.  Ewen  says : 

"My  experience  has  taught  me  that  it  is  almost  impossible 
to  determine  any  definite  data  of  cost  for  this  work.  This  is 
due  to  the  fact  that  no  two  caisson  jobs  will  average  the  same 
cost,  notwithstanding  the  fact  that  the  cost  of  material  used 
and  the  labor  conditions  are  exactly  the  same.  This  condition 


CONCRETE    PILE    FOUNDATIONS.  167 

is  due  to  the  great  variety  in  texture  of  the  soil  gone  through. 
For  instance,  it  has  come  under  my  experience  that  in  caissons 
of  the  same  diameter  on  the  same  job  it  required  but  fifteen 
8-hour  shifts  to  reach  bedrock  in  some  of  these,  while  it  re- 
quired as  many  as  21  to  25  shifts  to  reach  rock  in  the  others, 
rock  being  at  the  same  elevation.  In  fact,  the  digging  all  the 
way  to  rock  in  some  was  the  best  that  could  be  wished  for, 
while  in  the  others  boulders  and  quicksand  were  encountered, 
and  the  progress  was  slower,  and  the  cost  consequently 
greater. 

''Again,  we  have  known  it  to  require  eight  hours  for  two  men 
to  dig  8  ins.  in  hardpan  in  one  caisson,  while  on  a  job  going  on 
at  the  same  time  and  on  the  opposite  corner  of  the  street  two 
men  made  progress  of  2  ft.  in  8  hours  through  apparently  the 
same  stuff,  the  depth  of  hardpan  from  grade  being  61  ft.  6  ins. 
in  both  instances,  and  the  quality  of  labor  exactly  the  same. 

"There  have  been  more  heavy  losses  among  contractors  due 
to  the  unexpected  conditions  arising  in  caisson  digging  than 
in  any  other  item  of  their  work,  and  I  predict  a  loss  to  some  of 
them  that  will  be  serious  indeed  if  an  attempt  be  made  to  base 
future  bids  for  caisson  work  entirely  upon  the  data  kept  by 
them  on  past  work.  If  a  contractor  is  fortunate  enough  to 
find  the  ordinary  conditions  existing  in  his  caisson  work,  and 
by  ordinary  conditions  I  mean  few  boulders,  no  quicksand, 
ordinary  hardpan  and  no  gas,  the  following  items  may  be  con- 
sidered safe  for  figuring  caisson  work: 

"Figure  that  it  will  require  from  22  to  25  shifts  of  8  hours 
each  to  strike  bedrock,  bedrock  being  from  90  to  95  ft.  below 
datum,  and  datum  being  15  ft.  below  street  grade;  figure  2 
diggers  to  the  shift  in  all  caissons  over  5  ft.  in  diameter,  45  cts. 
per  hour  for  each  digger ;  figure  I  top  man  at  40  cts.  per  hour, 
and  i  mucker  or  common  laborer  at  30  cts.  per  hour  for  all 
caissons  in  which  there  are  two  diggers,  and  I  top  man  less  if 
i  digger  is  in  the  caisson,  which  condition  exists  generally  in 
caissons  less  than  5  ft.  in  diameter.  Add  the  cost  of  ^-in. 
cable,  tripods,  sheaves,  i-in.  Hauser  laid  line,  nigger  heads, 
ball-bearing  blocks,  etc.,  for  rigging  of  the  job.  Lagging, 
which  is  2  x  6  ins.  and  3x6  ins.  hemlock  or  some  hard  wood, 
in  length  of  5  ft.  4  ins.  and  4  ft.,  is  priced  all  the  way  from  $20 
to  $22.50  and  $21  to  $24.50  per  M.  ft.  B.  M.,  respectively.  The 


168  CONCRETE    CONSTRUCTION. 

price  of  caisson  rings  is  $2.49  per  100  Ibs.  The  cost  of  specially 
made  grubs  for  digging  in  hardpan  is  about  $26  per  dozen. 
Shovels  are  furnished  by  the  diggers  themselves  in  Chicago, 
111.  The  cost  of  temporary  electric  light  is  $10  per  caisson. 
This  includes  cost  of  cable,  lamps,  guards,  etc.  Add  the  cost 
of  or  rental  of  engine  or  motors  for  power. 

"Some  engineers  specify  three  rings  to  be  used  to  each  set 
of  lagging  below  the  top  set  until  hardpan  is  reached,  then  two 
rings  for  each  of  the  remaining  sets  from  hardpan  to  rock. 
This  is,  of  coarse,  to  insure  against  disaster  from  great  pres-' 
sure  of  the  swelling  clay  above  the  hardpan  strata,  and  may 
or  may  not  be  necessary.  These  rings  are  24  x  3  ins.  wrought 
iron. 

"For  caissons  which  are  not  specified  to  go  to  rock,  it  is  not 
considered  economical  to  rig  up  cable  set-ups,  but  rather  to 
use  windlass  derricks.  In  this  case  i-in.  Hauser  laid  line  is 
used  as  the  means  of  hoisting  the  buckets  of  clay  out  of  the 
caisson,  as  is  the  case  in  cable  set-ups,  hand  power  being  used 
on  the  windlass  derricks  instead  of  steam  or  electricity.  The 
windlass  derricks  are  made  with  four  legs  out  of  6  x  6-in.  yel- 
low pine  lumber.  The  top  piece  is  generally  a  piece  of  3  x  6-in. 
lagging.  The  cost  of  windlass  and  boxes  is  about  $35  per 
dozen.  Hooks  for  caisson  buckets  cost  45  cts.  each.  Cais- 
son buckets  cost  $8  each. 

"With  the  above  approximate  units  as  a  basis,  I  have  seen 
unit  prices  given  per  lineal  foot  in  caisson  work  which  ranged 
all  the  way  from  $12  to  $16.50  for  6-ft.  diameter  caissons, 
larger  and  smaller  sized  caissons  being  graded  in  price  accord- 
ing to  their  size.  This  unit  price  included  rings,  lagging,  con- 
crete, power,  light,  labor,  etc." 

From  the  above  data  the  following  figures  of  cost  can  be 
arrived  at,  assuming  a  6-ft.  caisson : 

Labor.  Per  day. 

2  diggers  in  caisson,  at  $3.60 $  7.20 

i  top  man,  at  $3.20 3.20 

I  mucker,  at  $2./.o 2.40 

$12.80 

The  depth  sunk  varies  from  3^  to  8  ft.  per  8-hour  day,  de- 
pending on  the  material.  Assuming  an  average  of  4  ft.,  we 


CONCRETE    PILE    FOUNDATIONS. 

have  then  4  lin.  ft.  of  caisson,  or  2.8  cu.  yds.  excavated  at  a 
labor  cost  of  $12.80,  which  is  at  the  rate  of  $3.20  per  lin.  ft.,  or 
$4.57  per  cu.  yd.  We  now  get  the  following: 

Per  lin.  ft. 
Caisson. 

40  ft.  B.  M.  (2x6-in.  lagging)  at  $25 $1.00 

60  Ibs.  iron  (34x3~in.  rings)  at  2^c 1.50 

0.7  cu.  yd.  excavation  at  $4.57 3.20 

0.7  cu.  yd.  muck  hauled  away  at  $i 0.70 

0.7  cu.  yd.  concrete  at  $5 3.50 

Electric  light o.io 

Total    $10.00 

If  3x6-in.  lagging  is  used  add  50  cts.  per  lin.  ft.  of  caisson. 

MOLDING  PILES  FOR  DRIVING.— Piles  for  driving  are 
molded  like  columns  in  vertical  forms  or  like  beams  in  hori- 
zontal forms.  European  constructors  have  a  strong  preference 
for  vertical  molding,  believing  that  a  pile  better  able  to  with- 
stand the  strain  of  driving  is  so  produced;  such  lamination  as 
results  from  tamping  and  settling  is,  in  vertical  molding,  in 
planes  normal  to  the  axis  of  the  pile  and  the  line  of  driving 
stress.  Vertical  molding  has  been  rarely  employed  in  America 
and  then  only  for  molding  round  piles.  The  common  belief  is 
that  horizontal  molding  is  the  cheaper  method.  In  the  ordi- 
nary run  of  work,  where  comparatively  few  piles  are  to  be 
ma.de,  it  is  probably  cheaper  to  use  horizontal  molds,  but 
where  a  large  number  of  piles  is  to  be  made,  the  vertical 
method  has  certain  economic  advantages  which  are  worth 
considering. 

Vertical  molding  necessitates  a  tower  or  staging  to  support 
the  forms  and  for  handling  and  placing  the  concrete ;  an  ex- 
ample of  such  a  staging  is  shown  by  Fig.  59.  To  counter- 
balance this  staging,  horizontal  molding  necessitates  a  molding 
platform  of  very  solid  and  rigid  construction  if  it  is  to  endure 
continued  and  repeated  use.  In  the  matter  of  space  occupied 
by  molding  plant,  vertical  molding  has  the  advantage.  A  tower 
40  ft.  square  will  give  ample  space  around  its  sides  for  80 
vertical  forms  for  12-in.  piles  and  leaves  I  ft.  of  clear  working 
space  between  each  pair  of  forms.  The  ground  area  occupied 
by  this  tower  and  the  forms  is  1,764  sq.  ft.  With  the  same 


170 


CONCRETE    CONSTRUCTION. 


spacing  of  molds  a  horizontal  platform  at  least  25x160  ft.  = 
4,000  sq.  ft.,  would  be  required  for  the  molds  for  the  same 
number  of  piles  25  ft.  long.  For  round  piles,  vertical  mold- 
ing permits  the  use  of  sectional  steel  forms ;  horizontal  forms 
for  round  piles  are  difficult  to  manage.  For  square  piles  ver- 
tical molding  requires  forms  with  four  sides ;  horizontal  forms 
for  square  piles  consist  of  two  side  pieces  only,  the  molding 


Fig.    59.— Plant   for  Vertical   Molding  of  Concrete   Piles. 

platform  serving  as  the  bottom  and  no  top  form  being  neces- 
sary. Thus,  for  square  piles  horizontal  molding  reduces  the 
quantity  of  lumber  per  form  by  50  per  cent.  The  side  forms 
for  piles  molded  on  their  sides  can  be  removed  much  sooner 
than  can  the  forms  for  piles  molded  on  end,  so  that  the  form 
material  is  more  often  released  for  reuse.  The  labor  of  assem- 


CONCRETE    PILE    FOUNDATIONS.  171 

bling  and  removing  forms  is  somewhat  less  in  horizontal 
molding  than  in  vertical  molding.  Removing  the  piles  from 
molding  bed  to  storage  yard  for  curing  requires  derricks  or 
locomotive  cranes  in  either  case  an-d  as  a  rule  this  operation 
will  be  about  as  expensive  in  plant  and  labor  in  one  case  as  in 
the  other.  In  the  ease  and  certainty  of  work  in  placing  the 
reinforcement,  horizontal  molding  presents  certain  advantages, 
the  placing  and  working  of  the  concrete  around  the  reinforce- 
ment is  also  easier  in  horizontal  molding.  Mixing  and  trans- 
porting the  concrete  materials  and  the  concrete  is  quite  as 
cheap  in  vertical  molding  as  in  horizontal  molding.  If  any- 
thing, it  is  cheaper  with  vertical  molding,  since  the  mixer  and 
material  bins  can  be  placed  within  the  tower  or  close  to  one 
side  where  a  tower  derrick  can  hoist  and  deposit  the  concrete 
directly  into  the  molds.  Car  tracks,  cars,  runways  and  wheel- 
barrows are  thus  done  away  with  in  handling  the  concrete 
from  mixer  to  molds.  Altogether,  therefore,  the  choice  of  the 
method  of  molding  is  not  to  be  decided  off-hand. 

DRIVING  MOLDED  PILES.— Driving  molded  concrete 
piles  with  hammer  drivers  is  an  uncertain  operation.  It  has 
been  done  successfully  even  in  quite  hard  soils  and  it  can  be 
done  if  time  is  taken  and  the  proper  care  is  exercised.  The 
conditions  of  successful  hammer  driving  are:  Perfect  align- 
ment of  the  pile  with  the  line  of  stroke  of  the  hammer;  the 
use  of  a  cushion  cap  to  prevent  shattering  of  the  pile-head,  and 
a  heavy  hammer  with  a  short  drop.  The  pile  itself  must  have 
become  well  cured  and  hardened.  At  best,  hammer  driving 
is  uncertain,  however ;  shattered  piles  have  frequently  to  be 
withdrawn  and  the  builder  is  never  sure  that  fractures  do  nol 
exist  in  the  portion  of  the  pile  that  is  underground  and  hid- 
den. The  actual  records  of  concrete  pile  worl  given  in  suc- 
ceeding sections  illustrate  successful  examples  of  hammer 
driving.  The  plant  required  need  not  vary  from  that  ordi- 
narily used  for  driving  wooden  piles,  except  that  more  power 
must  be  provided  for  handling  the  heavier  concrete  pile  and 
that  means  must  be  provided  for  holding  the  pile  in  line  and 
protecting  its  head. 

Sinking  concrete  piles  by  means  of  water  jets  is  in  all  re- 
spect a  process  similar  to  that  of  jetting  wooden  piles.  Exam- 
ples of  jetting  are  given  in  succeeding  section.  In  rare  cases, 


172 


CON-CRETE    CONSTRUCTION. 


driving  shells,  or  sheaths  have  been  used  for  driving  molded 
piles. 

Method  and  Cost  of  Molding  and  Jetting  Piles  for  an  Ocean 
Pier. — In  reconstructing  in  reinforced  concrete  the  old  steel 
pier  at  Atlantic  City,  N.  J.,  some  116  reinforced  concrete  piles 
12  ins.  in  diameter  were  molded  in  air  and  sunk  by  jetting. 
The  piles  varied  in  length  with  the  depth  of  the  water,  the 
longest  being  34^  ft.  Their  construction  is  shown  by  Fig. 
60,  which  also  shows  the  floor  girders  carried  by  each  pair  of 
piles  and  forming  with  them  a  bent,  and  the  struts  bracing  the 


Section  Cr  D 

Fig.   60.— Concrete  Pile  for  Pier  at  Atlantic  City,   N.  J. 
bents  together.     In  molding  and  driving  the  piles  the  old  steel 
pier  was  used  as  a  working  platform. 

The  forms  for  the  piles  were  set  on  end  on  small  pile  plat- 
forms located  close  to  the  positions  to  be  occupied  by  the  piles 
and  were  braced  to  the  old  pier.  The  forms  were  of  wood 
and  the  bulb  point,  the  shaft  and  the  knee  braces  were  molded 
in  one  piece.  Round  iron  rods  were  used  for  reinforcement. 
The  concrete  was  composed  of  i  part  Vulcanite  Portland  ce- 
ment, 2  parts  of  fine  and  coarse  sand  mixed  and  4  parts  of 
gravel  I  in.  and  under  in  size.  The  mixture  was  made  wet  and 
was  puddled  into  the  forms  with  bamboo  fishing  rods,  which 


CONCRETE    PILE    FOUNDATIONS. 


173 


proved  very  efficient  in  working  the  mixture  around  the  rein- 
forcing rods  and  in  getting  a  good  mortar  surface.  The  con- 
crete was  placed  in  small  quantities;  it  was  mostly  all  hand 
mixed.  The  forms  were  removed  in  from  5  to  7  days,  depend- 
ing on  the  weather. 

The  piles  were  planned  to  be  sunk  by  water  jet  and  to  this 
end  had  molded  in  them  a  2-in.  jet  pipe  as  shown.  They  were 
sunk  to  depths  of  from  8  ft.  to  14  ft.  into  the  beach  ?and. 
Water  from  the  city  water  mains  at  a  pressure  of  65  Ibs.  per 
sq.  in.  was  used. for  jetting;  this  water  was  furnished  under 
special  ordinance  at  a  price  of  $i  per  pile,  and  a  record  of  the 
amount  used  per  pile  was  not  kept.  The  piles  were  swung 
from  the  molding  platforms  and  set  by  derricks  and  block  and 
fall.  The  progress  of  jetting  varied  greatly  owing  to  obstruc- 
tions in  places  in  the  shape  of  logs,  old  iron  pipes,  etc.  In 
some  cases  several  days  were  required  to  get  rid  of  a  single 
pipe.  In  clear  sand,  with  no  obstruction,  a  12-in.  pile  could 
be  jetted  down  at  the  rate  of  about  8  ft.  per  hour,  working  I 
foreman  and  6  men.  The  following  is  the  itemized  actual 
cost  of  molding  and  sinking  a  26-ft.  pile  with  bulb  point  and 
knee  braces  complete: 

Cost  per 

Forms —  pile. 

Lumber,  340  ft.  B.  M.  @  $30 $10.20      

Labor  (carpenters  @  $2.50  per  day)   12.00      

Oil,  nails,  oakum,  bolts,  clamps,  etc 1.20      

$23.40  $  3.90 

Times  used 6      

Reinforcement — 

-?75  Ibs.  of  plain  fa-in.  steel  rods  @  2  cts.  per  lb..$  5.50      

Preparing  and  setting,  4/10  et.  per  Ib i.io  6.60 

Jet  Pipe— 

26l/»  ft.  of  2-in.  pipe  (ft>  10  cts.  per  ft.  in  place 2.65 

Setting  Forms— 

6  men  @  $2.50  per  day  =  $15,  set  4  piles 3-75 

Material — 

90/100  cu.  yds.  gravel  (a  $i-5O^per  yd 1.35      

45/100  cu.  yds.  sand  @  $1.50  per  yd 67      

1.50  bbls.  cement  @  $1.60 2.40  4.42 


174  CONCRETE    CONSTRUCTION. 

Labor — 

Concrete  and  labor  foreman   3.00 

6  laborers,  mixing  and  placing  by  hand,  $1.75 

each    10.50 


$13-50        3-38 
Average  number  of  piles  concreted  per  day.  ...          4      

Removing  Forms — 
4  men  @  $2.50  remove  and  clean  in  half  day  4 

columns 1.25 

-I  man  @  $2.25  plastering  column  with  cement 

grout  (4  per  day) .56 

Jetting  10  ft.  into  Sand — 

Foreman   $  3.00      

4  men,  $2.25  each,  handling  hose  and  traveler.  .     9.00      ..... 

$12.00  3.00 

Average  number  of  piles  jetted  per  day 4      

City  water  pressure  used  for  jetting  @  $i  per  pile    ....  i.oo 

Superintendence  (ft<  $5.00  per  day 1.25 

Caring  for  trestle,  traveler,  material,  etc 4.84 

Total  cost  per  pile $36.60 

The  pile  being  26  ft.  long,  the  cost  in  place  was  $1.41  per 
foot.  Subtracting  the  cost  of  sinking  amounting  to  $7.09  per 
pile,  we  have  the  cost  of  a  26-ft.  pile  molded  and  ready  to 
sink  coming  to  about  $1.10  per  foot.  It  should  be  noted  that 
this  is  the  cost  for  a  pile  of  rather  complicated  construction ; 
a  plain  cylindrical  pile  should  be  less  expensive. 

Method  of  Molding  and  Jetting  Square  Piles  for  a  Building 
Foundation. — The  foundation  covered  about  an  acre.  The  soil 
was  a  deposit  of  semi-fluid  mud  and  quicksand  overlying  a 
very  irregular  rock  bottom  and  encircled  by  a  ledge  of  rock. 
The  maximum  depth  of  the  mud  pocket  was  40  ft.,  and  in- 
terspersed were  floating  masses  of  hard  pan.  Soundings 
were  made  at  the  locations  of  all  piles ;  a  ^-in.  gas  pipe  was 
coupled  to  a  hose  fed  by  city  pressure  and  jetted  down  to  rock, 
the  depth  was  measured,  the  sounding  was  numbered  and  the 
pile  was  molded  to  length  and  numbered  like  the  sounding.  Tn 
all  414  piles  were  required,  ranging  in  length  from  il/>  to  40 


CONCRETE    PILE    FOUNDATIONS.  175 

ft. ;  all  piles  up  to  6  ft.  were  built  in  place  in  wooden  forms. 
The  piles  were  13  ins.  square  and  were  of  1-2^2-4  concrete  re- 
inforced with  welded  wire  fabric.  A  tin  speaking  tube  was 
molded  into  each  pile  at  the  center.  This  tube  was  stopped 
about  10  ins.  from  the  head  and  by  means  of  an  elbow  and 
threaded  nipple  projected  through  the  side  of  the  pile  to  allow 
of  attaching  a  pressure  hose.  The  piles  were  handled  to  the 
pile  driver,  the  hose  attached  and  water  supplied  at  100  Ibs. 
pressure  by  a  pump.  Churning  the  pile  up  and  down  aided 
the  driving.  A  hammer  was  used  to  force  the  piles 
through  the  hard  pan  layers.  A  wooden  follower  was  used  to 
protect  the  pile  head.  A  2,8oo-lb.  hammer  falling  20  ft.  did 
not  injure  the  piles.  One  pile  was  given  300  blows  with  a 
2,8oo-lb.  hammer  falling  12  ft.,  and  when  pulled  was  unbroken. 
It  was  found  that  30  ft.  piles  ?nd  under  could  be  picked  up 
safely  by  one  end ;  longer  piles  cracked  at  the  center  when 
so  handled.  These  long  piles  were  successfully  handled  by  a 
long  chain,  one  end  being  wrapped  around  the  pile  at  the 
center  and  the  other  end  similarly  wrapped  near  the  head ; 
the  hook  of  the  hoisting  fall  was  hooked  into  the  loop  of  the 
chain  and  as  the  pile  was  hoisted  the  hook  slipped  along  the 
chain  toward  the  top  gradually  up  ending  the  pile.  The  piles 
weighed  175  Ibs.  per  lin.  ft.  It  was  attempted  to  mold  the 
piles  directly  on  the  ground  by  leveling  it  off  and  covering  it 
with  tar  paper,  but  the  ground  settled  and  the  method  proved 
impracticable. 

Method  of  Molding  and  Jetting  Piles  for  Building  Founda- 
tions.— In  a  number  of  foundations  Mr.  Frank  B.  Gilbreth  has 
used  a  polygonal  pile,  either  octagonal  or  hexagonal,  with  the 
sides  corrugated  or  fluted  as  indicated  in  Fig.  61.  In  longi- 
tudinal section  these  piles  have  a  uniform  taper  from  butt  to 
point  and  have  flat  points.  Each  pile  is  cored  in  the  center, 
the  core  being  4  ins.  in  diameter  at  the  top  and  2  ins.  at  the 
bottom  end.  On  each  of  the  octagon  or  hexagon  sides  the  pile 
has  a  half-round  flute  usually  from  2l/2  to  3  ins.  in  diameter. 
The  principal  object  of  these  flutes  or  "corrugations"  is  to 
give  passage  for  the  escape  to  the  surface  of  the  water  forced 
through  the  center  core  hole  in  driving  the  pile.  They  are 
also  for  the  purpose  of  increasing  the  perimeter  of  the  pile  and 
thereby  gaining  greater  surface  for  skin  friction. 


176  CONCRETE    CONSTRUCTION, 

The  piles  are  reinforced  longitudinally  and  transversely.  On 
this  particular  job  the  reinforcement  was  formed  with  Clinton 
Electrically  Welded  Fabric,  the  meshes  being  3  ins.  x  12  ins. ; 
the  longer  dimension  being  lengthwise  with  the  pile  and  of 
No.  3  wire ;  the  horizontal  or  transverse  reinforcement  being 
of  No.  10  wire.  The  meshes  being  electrically  welded  to- 
gether, the  reinforcement  was  got  out  from  a  wide  sheet  tak- 
ing the  form  of  a  cone.  No  part  of  the  reinforcement  was 
closer  than  I  in.  from  the  outside  of  the  concrete.  In  general 
only  sufficient  sectional  area  of  material  is  put  in  the  reinforce- 
ment to  take  the  tensile  stresses  caused  by  the  bending  action 
when  handling  the  pile  preparatory  to  driving;  more  rein- 
forcement than  this  only  being  necessary  when  the  piles  are 
used  for  wharves,  piers  or  other  marine  structures,  where  a 
considerable  length  of  pile  is  not  supported  sidewise  or  when 
they  are  subjected  to  bending  stresses. 


Fig.    61.— Cross-Section    of    Corrugated    Reinforced    Concrete    Pile. 

Molding. — The  forms  for  molding  the  piles  are  made  from 
2-in.  stuff,  gotten  out  to  the  required  dimensions,  the  cor- 
rugations being  formed  by  nailing  pieces  on  the  inside  whose 
section  is  the  segment  of  a  circle.  The  sides  of  the  octagon 
are  fastened  to  the  ends  through  which  the  core  projects  some 
6  or  8  ins.  At  times  while  the  molding  of  the  pile  is  in  prog- 
ress, the  central  core  is  given  a  partial  turn  to  prevent  the 
setting  of  the  cement  holding  it  fast  and  thereby  preventing 
the  final  removal. 

The  stripping  of  the  forms  from  the  piles  is  usually  done 
from  24  to  48  hours  after  molding,  and  from  this  time  on  great 
care  is  taken  that  there  is  a  sufficient  amount  of  moisture  in 
the  pile  to  permit  of  the  proper  action  for  setting  of  the  ce- 
ment. This  is  usually  accomplished  by  covering  the  piles  over 
with  burlaps  and  saturating  with  water  from  a  hose ;  the 


CONCRETE    PILE    FOUNDATIONS. 


177 


operation   of  driving  the  pile  not  being  attempted  until  the 
concrete  is  at  least  ten  days  old. 

Driving. — The  operation  of  driving  corrugated  concrete 
piles  is  somewhat  similar  to  that  for  driving  ordinary  wooden 
piles  by  water  jet,  but  a  much  heavier  hammer  with  less  drop 
is  used.  The  jetting  is  accomplished  -by  inserting  a  2-in.  pipe 
within  the  pile.  This  pipe  is  tapered  at  the  bottom  end  to  i- 
in.  diameter,  forming  a  nozzle,  and  the  water  pressure  used  is 
about  120  Ibs.  per  sq.  in.  As  a  rule,  this  pressure  is  obtained 
by  the  use  of  a  steam  pump  which  may  be  connected  with  the 


Wooden  Buffer  X 


Hor.  Section  A-B. 

Fig.  62.— Cushion  Cap  for  Driving  Gilbreth    Corrugated  Pile. 

boiler  which  operates  the  pile  driver,  or  with  a  separate  steam 
supply.  At  the  upper  end  of  this  2-in.  pipe  an  elbow  is  placed 
and  a  short  length  of  pipe  is  connected  to  this  and  to  the  hose 
from  the  water  supply. 

As  it  is  not  practicable  to  drop  the  hammer  directly  on  the 
head  of  the  concrete  piles,  the  driving  is  accomplished  by  the 
use  !of  a  special  cap,  Fig.  62.  This  cap  is  about  3  ft.  in  height 
and  the  bottom  end  fits  over  the  head  of  the  pile.  In  one  side 
of  this  cap  is  a  slot  from  the  outside  to  the  center,  which  per- 
mits the  2-in.  pipe,  which  supplies  the  water  jet  for  driving  the 


CONCRETE    CONSTRUCTION.  ' 


pile,  to  project.  The  outside  of  this  cap  is  formed  with  a  steel 
shell,  the  inside  has  a  compartment  filled  with  rubber  packing 
and  the  top  has  a  wooden  block  which  receives  a  blow  from 
the  hammer.  In  this  way  the  head  of  the  pile  is  cushioned, 
which  prevents  the  blow  of  the  hammer  from  bruising  or 
breaking  the  concrete. 

During  the  operation  of  driving,  the  water  from  the  jet 
comes  up  on  the  outside  of  the  pile  and  carries  with  it  the 
material  which  it  displaces  in  driving.  This,  with  the  assis- 
tance of  the  hammer,  allows  the  pile  to  be  driven  in  place,  and, 
contrary  to  what  might  be  supposed,  after  the  operation  of 
driving  when  the  water  has  saturated  into  the  ground  or  been 
drained  away,  this  operation  puddles  the  earth  around  the 


Fig.    6:J. — View   Showing  Method   of  Fabricating  Reinforcement  for   a  Round 
'    Pile  with  Flattened  Sides. 

pile,  so  that  after  a  few  hours'  time  the  skin  friction  is  much 
more  than  it  would  be  with  the  pile  driven  into  more  compact 
soil  without  the  use  of  a  jet. 

Method  of  Molding  and  Driving  Round  Piles. — In  con- 
structing a  warehouse  at  Bristol,  England,  some  600  spirally- 
reinforced  piles  of  the  Coignet  type  were  used.  Coignet  piles 
are  in  section  circles  with  two  longitudinal  flat  faces  to  facili- 
tate guiding  during  driving ;  this  section  is  the  same  as  would 
be  found  by  removing  two  thin  slabs  from  opposite  sides  of  a 


CONCRETE    PILE    FOUNDATIONS.  179 

timber  pile.  The  reinforcement  consists  of  longitudinal  bars 
set  around  the  periphery  and  drawn  together  to  a  point  at 
one  end  and  then  inserted  into  a  conical  shoe ;  these  longi- 
tudinal bars  are  wound  spirally  with  a  *4-in.  rod  wire  tied  to 
the  bars  at  every  intersection.  This  spiral  rod  has  a  pitch  of 
only  a  few  inches,  but  to  bind  it  in  place  and  give  rigidity  to 
the  skeleton  it  is  wound  by  a  second  spiral  with  a  reverse 
twist  and  a  pitch  of  4  or  5  ft.  As  thus  constructed,  the  rein- 
forcing frame  is  sufficiently  rigid  to  bear  handling  as  a  unit. 
The  piles  used  at  Bristol  were  14  to  15  ins.  in  diameter  and 
52  ft.  long,  and  weighed  about  4  tons  gross  each.  The  mix- 
ture used  was  cement,  river  sand  and  crushed  granite. 

Molding. — In  molding  Coignet  piles  the  reinforcement  is 
assembled  complete  as  shown  by  Fig.  63  and  then  suspended 
as  a  unit  in  a  horizontal  mold  constructed  as  shown  by  the 


J 


Fig.    64.— Form   for   Molding  Round   Pile   with   Flattened    Sides. 

cross-section  Fig.  64.  The  concrete  is  deposited  in  the  lop 
opening  and  rammed  and  worked  into  place  around  the  steel 
after  which  the  opening  is  closed  by  the  piece  A.  After  24 
hours  the  curved  side  pieces  B  and  C  are  removed  and  the 
pile  is  left  on  the  sill  D  until  hard  enough  to  be  shifted;  a  pile 
is  considered  strong  enough  tor  driving  when  about  six  weeks 
old. 

Driving. — Coignet  piles  at  the  Bristol  work  were  handled  by 
a  traveling  crane.  The  material  penetrated  was  river  mud  and 
they  were  driven  with  a  hammer  weighing  2  tons  gross ;  in 
driving  the  pile  head  was  encircled  by  a  metal  cylinder  into 
which  fitted  a  wooden  plunger  or  false  pile  with  a  bed  of  shav- 
ings and  sawdust  between  plunger  and  pile  head. 

Molding  and  Driving  Square  Piles  for  a  Building  Founda- 
tion.— The  Dittman  Factory  Building  at  Cincinnati,  O.,  is 


180  CONCRETE    CONSTRUCTION. 

founded  on  reinforced  concrete  piles  varying  from  8  to  22  ft. 
in  length.  The  piles  were  square  in  cross-section,  with  a  2- 
in.  bevel  on  the  edges ;  a  i6-ft.  pile  was  10  ins.  square  at  the 
point  and  14  ins.  square  at  the  head,  shorter  or  longer  piles  had 
the  same  size  of  point,  but  their  heads  were  proportionally 
smaller  or  larger,  since  all  piles  were  cast  in  the  same  mold 
by  simply  inserting  transverse  partitions  to  get  the  various 
lengths.  Each  pile  was  reinforced  by  four  ^4-in.  twisted  bars, 
one  in  each  corner,  bound  together  by  J/^-in  hoops  every  12 
ins..  The  bars  were  bent  in  at  the  point  and  inserted  in  a 
hollow  pyramidal  cast  iron  shoe  weighing  about  50  Ibs.  The 
concrete  was  a  1-2-4  stone  mixture  and  the  pile  was  allowed  to 
harden  four  weeks  before  driving.  They  were  cast  horizontally 
in  wooden  molds  which  were  removed  after  30  hours. 

Driving. — Both  because  of  their  greater  weight  and  because 
of  the  care  that  had  to  be  taken  not  to  shatter  the  head,  it  took 
longer  to  adjust  and  drive  one  of  these  concrete  piles  than  it 
would  take  with  a  wooden  pile.  The  arrangement  for  driving 
the  piles  was  as  follows :  A  metal  cap  was  set  over  the  head 
of  the  pile,  on  this  was  set  the  guide  cap  having  the  usual 
wood  deadener  and  on  this  was  placed  a  wood  deadener  about 
i  ft.  long.  The  metal  cap  was  filled  with  wet  sand  to  form  a 
cushion,  but  as  the  pile  head  shattered  in  driving  the  sand 
cushion  was  abandoned  and  pieces  of  rubber  hose  were  sub- 
stituted. With  this  rubber  cushion  the  driving  was  accom- 
plished without  material  damage  to  the  pile  head.  The  ham- 
mer used  weighed  4,000  Ibs.  and  the  drop  was  from  4  to  6  ft. 
The  blows  per  pile  ranged  from  60  up.  The  average  being 
about  90.  In  some  cases  where  the  driving  was  hard  it  took 
over  400  blows  to  drive  a  14-ft.  pile.  An  attempt  to  drive  one 
pile  with  a  i6-ft.  drop  resulted  in  the  fracture  of  the  pile. 

Method  of  Molding  and  Driving  Octagonal  Piles. — The 
piles  were  driven  in  a  sand  fill  18  ft.  deep  to  form  a  foundation 
for  a  track  scales  in  a  railway  yard.  They  were  octagonal 
and  16  ins.  across  the  top,  16  ft.  long,  and  tapered  to  a  diam- 
eter of  12  ins.  at  the  bottom.  They  were  also  pointed  for  about 
a  foot.  The  reinforcement  consisted  of  four  */2-in.  Johnson 
corrugated  bars  spaced  equally  around  a  circle  concentric  with 
the  center  of  the  pile,  the  bars  being  kept  il/2  ins.  from  the 
surface  of  the  concrete.  A  Xo.  n  wire  wrapped  around  the 


CONCRETE    PILE    FOUNDATIONS. 


181 


outside  of  the  bars  secured  the  properties  of  a  hooped-concrete 
column.  The  piles  were  cast  in  molds  laid  on  the  side.  They 
were  made  of  i  14^2  gravel  concrete,  and  were  seasoned  at 
least  three  weeks  before  being  driven. 

An  ordinary  derrick  pile  driver,  with  a  2,5OO-lb.  hammer 
falling  18  ft.,  was  used  in  sinking  them.  A  timber  follower  6 
ft.  long  and  banded  with  iron  straps  at  both  ends  was  placed 
over  the  head  of  the  pile  to  receive  directly  the  hammer  blows. 
The  band  on  the  lower  end  was  10  ins.  wide  and  extended  6 
ins.  over  the  end  of  the  follower.  In  this  6-in.  space  a  thick 
sheet  of  heavy  rubber  was  placed,  coming  between  the  head 
of  the  pile  and  the  follower.  Little  difficulty  was  experienced 
in  driving  the  piles  in  this  manner,  although  250  to  300  blows 
of  the  hammer  were  required  to  sink  each  pile.  The  driving 


Fig.    65.— Cross-Section    of 
Chenoweth    Rolled   Pile. 


Fig.    66. — Diagram    Showing    Method 
of    Rolling    Chenoweth    Pile. 


being  entirely  through  fine  river  sand  there  is  every  proba- 
bility that  any  kind  of  piles  would  have  been  driven  slowly. 
The  heads  of  the  first  4  or  5  piles  were  battered  somewhat, 
but  after  the  pile  driver  crew  became  familiar  with  the  method 
of  driving,  no  further  battering  resulted  and  the  heads  of  most 
of  the  piles  were  practically  uninjured. 

Method  and  Cost  of  Making  Reinforced  Concrete  Piles  by 
Rolling. — In  molding  reinforced  concrete  piles  exceeding  30 
or  40  ft.  in  length,  the  problem  of  molds  or  forms  becomes  a 
serious  one.  A  pile  mold  50  or  60  ft.  long  is  not  only  expen- 
sive in  first  cost,  but  is  costly  to  maintain,  because  of  the  diffi- 
culty of  keeping  the  long  lagging  boards  from  warping.  To 
overcome  these  difficulties  a  method  of 'molding  piles  without 


1 82 


CONCRETE    CONSTRUCTION. 


forms  has  been  devised  and  worked  out  practically  by  Mr.  A. 
C.  Chenoweth,  of  Brooklyn,  N.  Y.  This  method  consists  in 
rolling  a  sheet  of  concrete  and  wire  netting  into  a  solid  cyl- 
inder on  a  mandril,  by  means  of  a  special  machine.  Fig.  65 
is  a  sketch  showing  a  cross-section  of  a  finished  pile,  in  which 
the  dotted  line  shows  the  wire  netting,  the  hollow  circle  is  the 
gas  pipe  mandril,  and  the  solid  circles  are  the  longitudinal  re- 
inforcing bars. 

In  making  the  pile  the  netting  is  spread  flat,  with  the  rein- 
forcing bars  attached  as  shown  at  (a),  Fig.  66,  and  is  then 
covered  with  a  layer  of  concrete.  One  edge  of  the  netting  is 


Fig.  67. — Machine  for  Rolling  Chenoweth  Piles. 

fastened  to  the  platform,  the  other  edge  is  attached  to  the 
winding  mandril.  The  winding  operation  is  indicated  by 
sketch  (&),  Fig.  66.  Fig.  67  shows  the  machine  for  rolling  the 
pile.  It  consists  of  a  platform  and  a  roll.  The  platform  is 
mounted  on  wheels  and  is  so  connected  up  that  it  moves  back 
under  the  roll  at  exactly  the  circumferential  speed  of  the  roll ; 
thus  the  forming  pile  is  under  constant,  heavy  pressure  be- 
tween the  roll  and  platform.  When  the  pile  has  been  com- 
pletely rolled  it  is  bound  at  intervals  by  wire  ties ;  the  wire 
for  these  ties  is  carried  on  spools  arranged  under  the  edge  of 


CONCRETE    PILE    FOUNDATIONS.  183 

the  platform  at  intervals  of  4  ins.  for  the  first  10  ft.  from  the 
point  and  of  6  ins.  for  the  remainder  of  the  length.  The  bind- 
ing is  done  by  giving  the  pile  two  or  three  extra  revolutions 
and  then  cutting  and  tying  the  wire ;  then  by  means  of  a  long 
removable  shelf  which  contains  the  flushing  mortar,  as  the 
pile  revolves  it  becomes  coated  On  the  outside  with  a  covering 
that  protects  the  ties  and  other  surface  metal.  Finally  the 
pile  is  rolled  onto  a  suitable  table  to  harden. 

An  exhibition  pile  rolled  by  the  process  described  is  61  ft. 
long  and  13  ins.  in  diameter.  This  pile  was  erected  as  a  pole 
by  hoisting  with  a  tackle  attached  near  one  end  and  dragging 
the  opposite  end  along  the  ground  exactly  as  a  timber  pole 
would  be  erected.  It  was  also  suspended  free  by  a  tackle  at- 
tached at  the  center;  in  this  position  the  ends  deflected  6  ins. 
Neither  "of  these  tests  resulted  in  observable  cracks  in  the  pile. 
The  pile  contains  eight  i-in.  diameter  steel  bars  61  ft.  long, 
one  2i/>-in.  pipe  also  61  ft.  long,  366  sq.  ft.,  or  40.6  sq.  yds.  ]/2- 
in.  mesh  14  B.  &  S.  gage  wire  netting,  and  2  cu.  yds.  loose 
concrete.  Its  cost  for  materials  and  labor  was  as  follows : 

Materials — 

Gravel,  28.8  cu.  ft.,  at  $i  per  cu.  yd $  1.05 

Sand,  19.8  cu.  ft.,  at  $i  per  cu.  yd 73 

Cement,  3  bbls.,  at  $1.60  per  bbl 4.80 

Netting,  40.6  sq.  yds.,  at  17^  cts.  per  sq.  yd 7.10 

Rods,  wire,  etc.,  1,826  Ibs.,  at  2l/2  cts.  per  Ib : 45.65 

Total     $59.33 

Mixing  2  cu.  yds.  concrete,  four  men  one  hour,  at  15  cts. 

per  hour $  0.60 

Placing  concrete  and  netting,  four  men  30  mins.,  at  15 

cts.  per  hour ,  .  .       .30 

Winding  pile,  four  men  20  mins.,  at  15  cts.  per  hour 20 

Removing  pile,  four  men  10  mins.,  at  15  cts.  per  hour.  .       .10 


$1.20 

Grand  total $60.53 

This  brings  the  cost  of  a  pile  of  the  dimensions  given  to 
about  $i  per  lin.  ft. 


CHAPTER  XI. 

METHODS  AND  COST  OF.  HEAVY  CONCRETE  WORK 
IN  FORTIFICATIONS,  LOCKS,  DAMS,  BREAK- 
WATERS AND  PIERS. 

The  construction  problem  in  building  concrete  structures  of 
massive  form  and  volume  is  chiefly  a  problem  of  plant  ar- 
rangement and  organization  of  plant  operations.  In  most 
such  work  form  construction  is  simple  and  of  such  character 
that  it  offers  no  delay  to  placing  the  concrete  as  rapidly  as  it 
can  be  produced.  The  same  is  true  of  the  character  of  the 
structure,  it  is  seldom  necessary  for  one  part  of  the  work  to 
wait  on  the  setting  and  hardening  of  another  part.  As  a  rule, 
there  is  no  reinforcement  to  fabricate  and  place  and  where 
there  is  it  is  of  such  simple  character  as  not  to  influence  the 
main  task  of  mixing,  handling,  and  placing  concrete.  Stated 
broadly,  the  contractor  in  such  work  generally  has  a  certain 
large  amount  of  concrete  to  manufacture,  transport  and  de- 
posit in  a  certain  space  with  nothing  to  limit  the  rapidity  of 
these  operations,  except  the  limitations  of  plant  capacity 
and  management.  Installation  and  operation  of  mixing  and 
conveying  plant,  then  are  matters  to  be  considered  carefully 
in  heavy  concrete  work. 

In  the  following  sections  we  have  given  one  or  more  ex- 
amples of  nearly  every  kind  of  heavy  concrete  work  excepting 
bridge  foundations  and  retaining  walls,  which  are  considered 
in  Chapters  XII  and  XIII,  and  except  rubble  concrete  work, 
which  is  considered  in  Chapter  VI.  In  each  case  so  far  as  the 
available  records  made  it  possible,  we  have  given  an  account 
of  the  plant  used  and  of  its  operation. 

FORTIFICATION  WORK.— Concrete  for  fortification 
work  consists  very  largely  of  heavy  platforms  and  walls  for 
gun  foundations  and  enclosures  and  of  heavily  roofed  gal- 
leries and  chambers  for  machinery  and  ammunition.  The 
work  is  very  massive  and  in  the  majority  of  cases  of  simple 

184 


LOCKS,   DAMS,   BREAKWATERS.  185 

form.  A  large  number  of  data  are  to  be  found  in  the  reports 
of  the  Chief  of  Engineers,  U.  S.  A.,  on  all  classes  of  fortifica- 
tion work,  but  the  manner  in  which  they  are  re- 
corded makes  close  analysis  of  relative  efficiencies  of 
methods  or  of  relative  costs  almost  impossible.  The  follow- 
ing data  are  given,  therefore,  as  examples  that  may  be  con- 
sidered fairly  representative  of  the  costs  obtained  in  fortifica- 
tion work  done  under  the  direction  of  army  engineers ;  these 
data  are  not  susceptible  of  close  analysis  because  wages,  work- 
ing force,  outputs,  etc.,  are  nearly  always  lacking. 

Gun  Emplacements,  Staten  Island,  N.  Y. — The  work  com- 
prised 5,609  cu.  yds.  of  concrete  in  two  12-in.  gun  emplace- 
ments, and  3,778  cu.  yds.  of  concrete  in  two  6-in.  gun  em- 
placements. Concrete  was  mixed  in  a  revolving  cube  mixer 
with  the  exception  of  809  cu.  yds.  in  the  6-in.  emplacements 
which  were  mixed  by  hand  at  a  cost  of  56  cts.  more  per  cubic 
yard  than  machine  mixing  cost.  The  body  of  the  concrete 
was  a  1-3-5  Portland  cement,  beach  sand  and  broken  trap 
rock  mixture.  The  floors  and  upper  surface  of  the  concrete 
had  a  pavement  consisting  of  6  ins.  of  1-3-5  concrete  surfaced 
with  2  ins.  of  1-3  mortar.  Wages  are  not  given,  but  for  the 
time  and  place  should  have  been  about  $1.50  per  8-hour  day 
for  common  labor.  The  cost  of  materials  was : 

Alpha  Portland  cement,  per  bbl.. $1.98 

Broken  trap  rock,  per  cu.  yd 0.81 

12-in.  emplacement,  hauling  sand  per  cu.  yd °-I75 

6-in.  emplacement,  hauling  sand  per  cu.  yd 0.20 

The  cost  of  the  concrete  in  place  was  as  follows : 

12-in.,  per  6-in.,  per 

Body  Concrete —  cu.  yd.       cu.  yd. 

Cement,   at   $1.98   per   bbl $2.546       $2.546 

Broken  stone,  at  81  cts.  per  cu.  yd 1.041         1.041 

Sand,  at  iy}/2  and  20  cts.  per  cu.  yd 0-225        °-257 

Receiving  and  storing  materials  at  n.6  cts.  per 

cu.  yd.  and  8.4  cts.  per  bbl 0.149         0.180 

Mixing,  placing  and  ramming 0.879         i.no 

Forms,,  lumber  and  labor  . O-477        0.950 

Superintendence  and  miscellaneous 0.190         0.150 

Total $5-507       $6.234 


1 86 


CONCRETE    CONSTRUCTION. 


Concrete  Pavement — 

Materials    ;. - $2.97 

Labor    /. 4.63 


$3-06 


Total    $7.60         $7.78 

Mortar  Battery  Platform,  Tampa  Bay,  Fla. — The  platform 
contained  8,994  cu.  yds.  of  concrete  composed  of  a  mixture  of 
Portland  cement,  sand,  shells  and  broken  stone.  The  broken 
stone  and  cement  were  brought  in  by  vessel  and  the  sand  and 
shells  were  obtained  from  the  beach  near  by.  The  plant  for 
the  work  was  arranged  as  shown  by  the  sketch,  Fig.  68.  Sand, 


Shell  Bcmtrs 


Fig.    68. — Sketch    Plans    of    Concrete    Making   Plant    for   Mortar   Battery 

Platform. 

stone  and  shells  were  stored  in  separate  compartments  in  the 
storage  bins.  Box  cars,  divided  into  compartments  of  such 
size  that  when  each  was  filled  with  its  proper  material,  the 
car  would  contain  the  proper  proportions  for  one  batch  of  con- 
crete, were  pushed  by  hand  under  the  several  compartments 
of  the  bin  in  succession  until  charged ;  then  they  were  hooked 
to  a  cable  and  hauled  to  the  platform  over  the  mixer  and 
dumped.  The  charge  was  then  turned  over  with  shovels  and 
shoveled  into  the  hopper  of  a  continuous  mixer,  located  be- 
neath. Two  cars  were  used  for  charging  the  mixer,  running 
on  separate  tracks  as  shown.  The  mixer  discharged  into 
buckets  set  on  flat  cars,  which  were  hauled  by  mules  under  the 
cableway,  which  then  lifted  and  dumped  the  bucket  and  re- 
turned it  empty  to  the  car.  By  using  three  bucket  cars,  one 


LOCKS,   DAMS,    BREAKWATERS.  187 

was  always  ready  to  receive  the  mixer  discharge  as  soon  as  the 
preceding  one  had  been  filled,  so  that  the  mixer  operated  con- 
tinuously. The  cableway  had  a  working  span  of  270  ft., 
the  cable  being  carried  by  traveling  towers  69  ft.  high  ;  the 
cableway  was  very  easily  operated  back  and  forth  along  the 
work.  The  cableway  complete,  with  497  ft.  of  six-rail  track 
for  each  tower,  cost  $4,700.  The  cost  of  materials  and  labor 
for  the  8,994  cu.  yds.  of  concrete  was  as  follows : 

Per  cu.  yd. 

i  bbl.  cement  at  $2.46 $2.46 

0.89  cu.  yd.  stone,  at  $2.95 2.622 

0.315  cu.  yd.  shells,  at  $0.45 0.142 

0.51  cu.  yd.  sand,  at  $0.12 0.062 

Mixing  and  placing 0-693 

Total    $5-979 

The  above  batch  tamped  in  place  to  30  cu.  ft.,  or  I  1/9  cu. 
yds.,  which  gives  the  cost  as  follows: 

Per  cu.  yd. 

Cost  of  concrete  tamped  in  place $5.381 

Cost   of  form   work    0.370 

Total  cost   $5-75 l 

In  the  preceding  prices  of  cement  and  stone,  59  cts.  and  29 
cts.  per  cubic  yard,  respectively,  are  included  for  storage.  The 
costs  of  sand  and  shells  are  costs  of  screening  and  storing. 
Rough  lumber  for  forms  cost  $10.25,  and  dressed  lumber 
$12.75  per  M.  ft.  B.  M. 

Emplacement  for  Battery,  Tampa  Bay,  Fla. — The  emplace- 
ment contained  6,654  cu.  yds.  of  Portland  cement,  sand,  shells 
and  broken  stone  concrete.  The  plant  arrangement  is  shown 
by  Fig.  69.  The  sand  and  shells  were  got  near  the  site,  using 
an  inclined  cableway  running  from  a  4O-ft.  mast  near  the 
mixer  to  a  deadman  at  the  shell  bank.  All  the  sand  for  the 
fill  around  the  emplacement  was  obtained  in  the  same  way. 
The  other  materials  were  brought  by  vessel  to  a  wharf,  loaded 
by  derrick  onto  cars  operated  by  an  endless  cable,  and  taken 
to  the  work.  The  storage  bins  and  mixing  plant  were  op- 
erated much  like  those  for  the  mortar  battery  work,  previously 


1 88 


CONCRETE    CONSTRUCTION. 


described.  A  cube  mixer  was  used,  and  the  concrete  was 
handled  from  it  to  the  work  by  a  crane  derrick  covering  a  cir- 
cle of  TOO  ft.  in  diameter.  The  cost  of  materials  and  concrete 
was  as  follows : 

Cement,  plus  7  cts.  for  storage  per  bbl $  2.532 

Stone,  pjus  38  cts.  for  storage  per  cu.  yd 3-O47 

Shells,  excavating  and  storage   0.481 

Sand,  excavating  and  storage   .v 0-250 

Lumber,  rough  per  M.  ft.  B.  M 10.25 

Lumber,  dressed  per  M.  ft.  B.  M 12.75 

A  batch  made  up  as  follows,  tamped  in  place  to  a  volume  of 
30  cu.  ft.  or  i  1/9  cu.  yds.: 


Fig.  69. — Sketch  Flans  of  Concrete  Making-  Plant  for  Battery  Emplacement. 

I  bbl.  cement,  at  $2.532 $  2.532 

0.315  cu.  yd.  shells,  at  $0.481 0.151 

0.51  cu.  yd.  sand,  at  $0.25   O-13° 

0.89  cu.  yd.  stone,  at  $3.047. 2.710 

Mixing  and  placing 0.761 

Total  for  30  cu  ft $6.284 

This  gives  a  cost  per  cubic  yard  of  concrete  in  place  as  fol- 
lows: 

Concrete  in  place,  per  cu.  yd $  5.655 

Forms,  per  cu.  yd.  of  concrete 0.220 


Total  cost  of  concrete  per  cu.  yd $  5.875 


LOCKS,   DAMS,   BREAKWATERS,  189 

United  States  Fortification  Work. — The  following  methods 
and  cost  of  mixing  and  placing  concrete  by  hand  and  by 
cubical  mixers  is  given  by  Mr.  L.  R.  Grabill  for  U.  S.  Gov- 
ernment fortification  work  done  in  1899. 

Hand  Miring  and  Placing. — The  work  was  done  by  con- 
tract, using  a  I  cement,  2  sand,  2  pebbles  and  3  stone  mixture 
turned  four  times.  A  board  large  enough  for  three  batches 
at  a  time  was  used;  one  batch  was  being  placed,  one  being 
mixed  and  one  being  removed  at  the  same  time  so  that  the 
mixers  moved  without  interval  from  one  to  the  other.  Two 
gangs  were  worked,  each  mixing  64  batches  of  0.75  cu.  yd., 
or  48  cu.  yds.  of  concrete  per  day  at  the  following  cost : 

Per         Per 

Hand  Mixing  9,000  Cu.  Yds. —  day.     cu.  yd. 

6  men  wheeling  materials   , $  7.50         $0.16 

8  men  mixing   10.00  0.21 

8  men  wheeling  away 10.00  0.21 

6  men  placing  and  ramming 7.50  0.16 

i   pump  man    1.25  0.02 

i  waterboy i.oo  0.02 

i  foreman    2.00          0.04 

Totals    $39.25         $0.82 

The  entire  cost  of  plant  for  this  work  was  about  $500. 
Machine  Mixing  and  Placing. — The  concrete  was  mixed  in 
a  4-ft.  cubical  mixer  operated  by  a  12  hp.  engine  which  also 
hauled  the  material  cars  up  the  incline  to  the  mixer.  These 
cars  passed  by  double  track  under  the  material  bins  where 
the  compartments  of  the  car  body  were  filled  through  trap 
doors ;  they  then  passed  the  cement  house  where  the  cement 
was  placed  on  the  load,  then  up  the  incline  to  the  mixer  and 
dumped,  and  then  empty  down  an  opposite  incline.  Seven 
turns  of  the  mixer  mixed  the  charge  which  was  discharged 
into  iron  tubs  on  cars  hauled  by  horses  to  two  derricks  whose 
booms  covered  the  work.  One  gang  by  day  labor  mixed  and 
placed  168  batches  of  0.7  cu.  yd.,  or  117.6  cu.  yds.  per  day  at 
the  following  cost : 


190 


CONCRETE    CONSTRUCTION. 


Per  Per 

Machine  Mixing  4,000  Cu.  Yds. —                     day.  cu.  yd 

32  men  at  $1.25   $40.00  $0.34 

i   pumpman    1.25  o.oi 

1  teamster  and  horse .- 2.00  0.02 

2  waterboys  at  $i 2.00  0.02 

i   engineman 1.70  0.02 

i   derrickman     1.50  o.oi 

i   fireman 1.50  o.oi 

i  foreman    . .  . ; 2.88  0.03 

Fuel   (cement  barrels  largely) 1.25  o.oi 

Totals    $54.o8  $0.47 

The  cost  of  the  plant  was  about  $5,000. 


Fig.    70. — Concrete    Making    Plant    for    Constructing-    Lock    Walls.    Cascades 

Canal. 

LOCK  WALLS,  CASCADES  CANAL.— Four-fifths  or 
70,000  cu.  yds.  of  lock  masonry  was  concrete,  the  bulk  of. 
which  was  mixed  and  deposited  by  the  plant  shown  by  Fig.  70. 
The  concrete  was  Portland  cement,  sand,  gravel  and  broken 
stone.  Cement  was  brought  in  in  barrels  by  railway,  stored 
and  tested ;  from  the  store  house  the  barrels  were  loaded  onto 
cars  and  taken  250  ft.  to  a  platform  onto  which  the  barrels 
were  emptied  and  from  which  the  cement  was  shoveled  into 
the  cement  hopper  and  chuted  to  cars  which  took  it  to  the 
charging  hopper  of  the  mixer.  The  stone  was  crushed  from 
spalls  and  waste  ends  from  the  stone  cutting  yards,  where 
stone  for  wall  lining  and  coping  and  other  special  parts  was 
prepared.  These  spalls  and  ends  were  brought  in  cars  and 


LOCKS,   DAMS,   BREAKWATERS.  191 

dumped  into  the  hopper  of  a  No.  5  Gates  crusher,  with  a 
capacity  of  30  tons  per  hour.  From  the  crusher  the  stone 
passed  to  a  2^/2 -in.  screen,  the  pieces  passing  going  to  a  bin 
below  and  the  rejections  going  to  a  smaller  Blake  crusher  and 
thence  to  the  bin.  The  dust  and  small  /  particles  were  not 
screened  out.  The  sand  and  gravel  were  obtained  by  screen- 
ing and  washing  pit  gravel.  The  gravel  was  excavated  and 
brought  in  cars  to  the  washer.  This  consisted  of  a  steel  cyl- 
inder 2  ft.  6l/2  ins.  in  diameter  and  about  18  ft.  long,  having 
an  inclination  of  i  in.  per  foot.  An  axial  gudgeon  supported 
the  cylinder  at  the  lower  end  and  it  rested  on  rollers  at  the 
other  end 'and  at  an  intermediate  point.  The  gravel  was  fed 
by  hopper  and  chute  into  the  upper  end  and  into  this  same 
end  a  3~in.  perforated  pipe  projected  and  extended  to  about 
mid-length  of  the  cylinder.  The  cylinder  shell  was  solid  and 
provided  with  internal  fins  for  about  half  its  length  from  the 
feed  end.  For  the  remainder  of  its  length  nearly  to  the  end, 
the  shell  was  perforated  with  2l/2-'m.  holes.  For  a  length  of  4 
ft.  beyond  mid-point  it  was  encircled  by  a  concentric  screen 
of  y%-m.  holes,  and  this  screen  for  3  ft.  of  its  length  was  en- 
circled by  another  screen  of  30  meshes  to  the  inch.  The  pit 
mixture  fed  into  the  cylinder  was  gradually  passed  along  by 
the  combined  inclination  and  rotation,  being  washed  and 
screened  in  the  process.  The  sand  fell  into  one  bin  and  the 
gravel  into  another,  and  the  waste  water  was  carried  away 
by  a  flume.  The  large  stones  passed  out  through  openings  at 
the  lower 'end  of  the  shell  and  were  chuted  into  cars.  The 
cars  came  to  the  mixer  as  clearly  shown  by  Fig.  70. 

The  stone  and  gravel  cars  were  side  dump  and  the  cement 
car  was  bottom  dump.  The  mixers  were  of  the  cube  type  4 
ft.  on  each  edge  and  operated  by  a  7  x  12-in.  double  cylinder 
engine  at  nine  revolutions  per  minute.  The  usual  charge  was 
32  cu.  ft.  of  the  several  ingredients,  and  it  was  found  that  15 
revolutions  requiring  about  il/2  minutes  were  sufficient  for 
mixing.  The  average  work  of  one  mixer  was  17  batches  or 
about  13  cu.  yds.  per  hour,  but  this  could  be  speeded  up  to  20 
batches  per  hour  when  the  materials  were  freely  supplied  and 
the  output  freely  removed.  Two  cars  took  the  concrete  from 
the  mixer  to  the  hopper,  from  which  it  was  fed  to  the  work 
by  chute.  The  hopper  was  mounted  on  a  truck  and  the  chute 


192  CONCRETE    CONSTRUCTION. 

was  a  wrought  iron  cylinder  trussed  on  four  sides  and  having 
a  45°  elbow  at  the  lower  end  to  prevent  scattering.  The  chute 
fed  into  a  car  running  along  the  wall  and  distributing  the 
material.  It  was  found  impracticable  to  move  the  chute  read- 
ily enough  to  permit  of  feeding  the  concrete  directly  into 
place.  As  the  concreting  progressed  upward  the  trestle  was 
extended  and  the  chute  shortened.  It  was  found  that  wear 
would  soon  disable  a  steel  chute  so  that  the  main  trussed 
cylinder  had  a  smaller,  cheaply  made  cylinder  placed  inside 
as  a  lining  to  take  the  wear  and  be  replaced  when  necessary. 

The  plant  described  worked  very  successfully/  Records 
based  on  9,614.4  cu.  yds.  of  concrete  laid,  gave  the  following : 

Cu.  yds. 

Concrete  mixed  by  hand  l>777'° 

Concrete  mixed  by  machine .7,837.4 

Total  concrete  laid 9,614.4 

Concrete  placed  by  derricks  2,372.0 

Concrete  placed  by  chute   7,242.4 

Concrete  1-2-4  mixture 156.0 

Concrete    1-3-6  mixture    1,564.0 

Concrete   1-4-8  mixture    6,892.0 

The  average  mixture  was  I  cement,  3.7  sand,  4.8  gravel  and 
2.6  broken  stone.  The  average  product  was  1.241  cu.  yds.  con- 
crete per  barrel  of  cement  and  1.116  cu.  yds.  of  concrete  per 
cubic  yard  of  stone  and  gravel.  The  average  materials  for 
i  cu.  yd.  of  concrete  were :  Cement  0.805  bbl.,  sand  0.456  cu. 
yd.,  gravel  0.579  cu-  7^-,  and  stone  0.317  cu.  yd. 

The  cost  of  these  9,614.4  cu.  yds.  of  concrete  in  place  was : 
Hand  Mixed  and  Placed  by  Derrick —  Per  cu.  yd. 

Labor  mixing  1,777  cu.  yds $1.072 

Repairs,  fuel,   etc    0.016 

Total   cost   mixing $1.088 

Labor  placing  2,372  cu.  yds 0.6025 

Fuel,  tramways,  etc 0.1958 

Total  cost  placing  $o.7983 


LOCKS,  DAMS,  BREAKWATERS.  193 

Machine  Mixed  and  Placed  by  Chute — 

Labor  mixing  7,837  cu.  yds .$0.388 

Repairs,  fuel,  etc 0.046 

Total  cost  mixing $0.434 

Labor  placing  7,242  cu.  yds.   0.414 

Fuel,  tramways,  etc 0.045 


Total  cost  placing  ............................  $0.459 

Materials  and  Supplies  9,614  cu.  yds.  — 
Timbering    ........................................  $0.145 

Cement    ...........................................   3.289 

Sand  and  gravel    ..................................    I-°73 

Broken  stone  ......................................   O-536 

Cement  testing,  repairs,  etc  ...................  .'....  0.223 

Total   ......  ..........  ........................  $5.266 

Plant  and  Superintendence,  9,614  Cu.  Yds.  — 
Engineering,  superintendence,  repairs,  etc  .............  $1.508 

20%  cost  of  plant  ..................................  0.165 

Total    .......................................  $1-673 

The  comparative  cost  of  hand  and    machine    mixing    and 
handling  was  thus  : 

Item  —  Hand.  Machine. 

Mixing  per  cu.  yd  ........................  $1.088         $0.434 

Placing  per  cu.  yd  ........................   0.798  0.459 

Materials,  etc.,  per  cu.  yd  ........  .  .........   5466          5.466 

Plant,  etc.,  per  cu.  yd  .....................    1.673 


Totals    .....  .  .....  .  ......  .  ..........  $9.025        $8.032 

The  average  total  costs  of  all  the  concrete  placed  were: 
Mixing  per  cu.  yd  .........................  .........  $°-555 

Placing  per  cu.  yd  ...................................  0.543 

Materials  per  cu.  yd  ........  .  ........................   5.266 

Plant,  etc.,  per  cu.  yd  ........................  .......    1.673 

Total  ........................................  $8.037 


194 


CONCRETE    CONSTRUCTION. 


LOCKS,  COOSA  RIVER,  ALABAMA.— The  following 
methods  and  costs  are  given  by  Mr.  Charles  Firth  for  con- 
structing lock  No.  31  for  the  Coosa  River  canalization,  Ala- 
bama. This  lock  is  420  ft.  long  over  all,  322  ft.  between 
quoins,  52  ft.  clear  width,  14.7  ft.  lift  and  8  ft.  depth  of  water 
on  sills;  it  contained  20,000  cu.  yds.  of  concrete  requiring  21,- 
500  bbls.  cement,  half  Alsen  and  half  Atlas. 

Figure  71  shows  the  concrete  mixing  plant,  consisting  of 
two  4x4  ft.  cube  mixer,  driven  by  a  10  x  i6-in.  engine.  The 
top  floor  of  the  mixer  house  stored  the  cement,  2,000  bbls.  The 
concrete  was  a  1-3-5^/2  stone  mixture.  Each  mixer  charge 
consisted  of  3  cu.  ft.  cement,  9  cu.  ft.  sand  and  16.5  cu.  ft. 


Fig.    71.— Concrete   Mixing  Plant   for   Lock  Construction,  Coosa  River. 

Alabama. 

stone ;  the  charge  was  turned  over  four  times  before  and  six 
times  after  watering  at  a  speed  not  exceeding  eight  revolu- 
tions per  minute.  The  average  output  of  the  plant  was  200 
cu.  yds.  per  8-hour  day,  or  100  cu.  yds.  per  mixer,  but  it  was 
limited  by  the  means  for  placing. 

The  concrete  was  mixed  dry,  deposited  in  6  to  8-in.  layers, 
and  rammed  with  3O-lb.  iron  rammers  with  6-in.  square  faces. 
For  all  exposed  surfaces  a  6-in.  facing  of  1-3  mortar  was 
placed  by  setting  2  x  12-in.  planks  4  ins.  from  the  laggings,  be- 
ing kept  to  distance  by  2  x  4-in.  spacers,  placing  and  ramming 
the  concrete  behind  them,  then  withdrawing  them,  filling  the 
6-in.  space  with  mortar  and  tamping  it  to  bond  with  the  con- 


LOCKS,  DAMS,   BREAKWATERS.  195 

crete.  The  walls  were  carried  up  in  lifts,  each  lift  being 
completed  entirely  around  the  lock  before  beginning  the  next ; 
the  first  lift  was  10.7  ft.  high  and  the  others  6  ft.,  except  the 
last,  which  was  4.5  ft.,  exclusive  of  the  i8-in.  coping.  The 
coping  was  constructed  of  separately  molded  blocks  3  ft.  long, 
made  of  1-2-3  concrete  faced  with  i-i  mortar  and  having  edges 
rounded  to  3  ins.  radius. 

In  constructing  the  forms  a  rdw  of  6  x  8-in.  posts  24  ft.  long 
and  5  to  7  ft.  apart  was  set  up  along  the  inside  of  each  wall 
and  a  similar  row  of  posts  12  ft.  long  was  set  up  along  the  out- 
side. From  the  tops  of  the  short  posts  6  x  8-in.  caps  reached 
across  the  wall  and  were  bolted  to  the  long  posts ;  these  caps 
carried  the  stringers  for  the  concrete  car  tracks.  The  lagging 
consisted  of  3  x  lo-in.  planks  dressed  on  all  sides.  The  backs 
of  the  walls  were  stepped  and  as  each  step  was  completed  the 
rear  12-ft.  posts  were  lifted  to  a  footing  on  its  top  and  car- 
ried in  the  necessary  distance.  The  front  posts  remained  un- 
disturbed until  the  wall  was  completed.  The  lagging  was 
moved  up  as  the  filling  progressed.  As  no  tie  bolts  were  per- 
mitted, these  forms  required  elaborate  bracing. 

From  the  mixing  plant,  which  was  located  on  the  bank 
above  reach  of  floods,  the  concrete  cars  were  dropped  by  ele- 
vator to  the  level  of  the  track  over  the  walls  and  then  run 
along  the  wall  and  dumped  onto  platforms  inside  the  forms 
and  just  below  the  track.  This  arrangement  was  adopted,  be- 
cause it  was  found  that  even  a  small  drop  separated  the  stone 
from  the  mortar.  The  concrete  was  shoveled  from  the  plat- 
forms to  place  and  rammed.  The  cars  were  bottom  dumping 
with  a  single  door  hinged  at  the  side;  this 'door  when  swinging 
back  struck  the  track  stringers  ajid  jarred  the  form  so  that 
constant  attention  was  necessary  to  keep  it  in  line.  It  would 
have  been  much  better  to  have*  had  double  doors  swinging 
endwise  of  the  car.  Another  point  noted  was  that  unless  the 
track  was  high  enough  to  give  good  head  room  at  the  close  of 
a  lift  the  placing  and  ramming  were  not  well  done. 

The  cost  of  8,710  cu.  yds.  of  concrete  placed  during  1895 
by  day  labor  employing  negroes  at  $i  per  8-hour  day  was  as 
follows  per  cubic  yard: 


I96  CONCRETE    CONSTRUCTION. 

i  bbf.   cement $2.48 

0.88  cu.  yd.  stone  at  $0.76   0.67 

0.36  cu.  yd.  sand  at  $0.34   0.12 

Mixing,    placing    and    ramming    0.88 

Staging  and  forms 0.42 


Total    $4-57 

LOCK  WALLS,  ILLINOIS  &  MISSISSIPPI  CANAL.— 

The  locks  and  practically  all  other  masonry  for  the  Illinois  & 
Mississippi  Canal  are  of  concrete.  The  following  account  of 
the  methods  and  cost  of  doing  this  concrete  work  is  taken 
from  information  published  by  Mr.  J.  W.  Woermann  in  1894 
and  special  information  furnished  by  letter.  The  decision  to 
use  concrete  was  induced  by  the  fact  that  no  suitable  stone  for 
masonry  was  readily  available  (the  local  stone  was  a  -flinty 
limestone,  usually  without  bed,  or,  at  best,  in  thin  irregular 
strata,  and  cracked  in  all  directions  with  the  cracks  filled  with 
fire  clay)  while  good  sand  and  gravel  and  good  stone  for 
crushing  were  plentifully  at  hand.  The  concrete  work  done  in 
1893-4  comprised  dam  abutments,  piers  for  Taintor  gates  and 
locks. 

Darn  Abutments. — Four  dam  abutments  were  constructed, 
three  of  which  were  L-shaped,  with  sides  next  to  the  river  40 
ft.  long  and  sides  extending  into  the  banks  20  ft.  long;  the  top 
thickness  was  3  ft.,  the  faces  were  vertical  and  the  backs 
stepped  with  treads  of  14  to  16  ins.,  and  the  width  of  base  was 
0.4  of  the  height.  Each  of  these  abutments  was  built  in  four 
3O-CU.  yd.  sections,  each  section  being  a  day's  work.  The 
forms  consisted  of  2  x  8-in.  planks,  dressed  on  both  sides,  2x8- 
in.  studs  spaced  2  ft.  on  centers  and  4x6-in.  braces.  For  the 
first. two  of  the  four  abutments,  the  forms  were  erected  in 
sections,  the  alternate  sections  being  first  erected  and  filled. 
When  these  sections  had  hardened  the  forms  were  shifted  to 
the  vacant  sections  and  lined  up  to  and  braced  against  the 
completed  sections.  This  method  did  not  give  well  aligned 
walls,  so  in  subsequent  work  the  forms  were  erected  all  at 
once. 

The  concrete  was  mixed  by  hand.  The  sand  and  cement 
were  mixed  dry,  being  turned  four  times  and  spread  in  a  layer. 


LOCKS,   DAMS,   BREAKWATERS. 


197 


Pebbles  and  broken  stone  previously  wetted  were  spread  over 
the  sand  and  cement  and  the  whole  turned  four  times,  the  last 
turn  being  into  wheelbarrows ;  about  five  common  buckets  of 
water  were  added  during  the  mixing.  The  mixture  sought 
was  one  that  would  ram  without  quaking.  Two  forms  of  ram- 
mers were  used ;  for  work  next  to  forms  a  4  x  6-in.  rammer 
and  for  inside  work  6-in  diameter  circular  rammer  weighing 
20  Ibs.  The  gang  mixing  and  placing  concrete  consisted 
usually  of; 

Item.  Per  Day.     Per  Cu.  Yd. 

2  handling  cement  and  sand $  3.00  $0.10 

3  filling  barrows  with  aggregate   4.50  0.15 

8  mixing  concrete    12.00  0.40 

2  shoveling  concrete  into  barrows 3.00  o.io 

5  wheeling  concrete  to  forms  7.50  0.25 

i  spreading  concrete  1.50  0.05 

5  tamping  concrete   7.50  0.25 

Total,  26  men  . . $39.00  $1.30 

These  cubic  yard  costs  are  based  on  30  cu.  yds.  of  wall  com- 
pleted per  8-hour  day.  The  cost  in  detail  of  two  abutments 
containing  254  cu.  yds.  was  per  cubic  yard  as  follows : 

Item.  PerCn.Yd. 

1.65  bbls.  Portland   (Germania)  cement $  5.60 

0.5  cu.  yd.  crushed  stone 2.07 

0.24  cu.  yd.  gravel 0.59 

0.53  cu.  yd.  sand 0.24 

Lumber,  forms,  warehouses,  platforms* 0.55 

Carpenter  workt  ($9  per  M.)   i.io 

Mixing  and  placing i-47 

20  per  cent,  first  cost  of  plant 0.31 

Engineering  and  miscellanies 0.31 

Total  .„ $12.24 

The  large  amount  of  cement  1.65  bbls.  per  cubic  yard  was 
due  to  facing  the  abutments  with  8  ins.  of  1-2  mortar.  The 
concrete  in  the  body  of  the  wall  was  I  cement,  2  sand,  2  gravel 


"Charging  %  of  first  cost  of  $18  per  M.   ft. 

fCarpenters   $3.50,   laborers   $1  50   per  day;   there  was  one  laborer  to  two 
carpenters. 


1 98 


CONCRETE    CONSTRUCTION. 


and  2  broken  stone  mixture.  A  dry  mixture  was  used  and  this 
fact  is  reflected  in  the  cost  of  ramming,  25  cts.  per  cu.  yd. 
The  cost  of  mixing  was  also  high. 

Piers  for  Taintor  Gates. — The  masonry  at  this  point  consist- 
ed of  three  piers  6x30  ft.,  and  two  abutments  30  ft.  long, 
6  ft.  thick  at  base  and  4  ft.  thick  at  top,  with  wing  walis ;  it 
amounted  to  460  cu.  yds.  The  feet  of  the  inclined  braces  were 
set  into  gains  in  the  horizontal  braces  and  held  by  an  8-in. 
lag  screw ;  after  the  posts  were  plumbed  a  block  was  lag- 
screwed  at  the  upper  end  of  each  brace.  These  forms  proved 
entirely  satisfactory.  The  cost  of  the  work  per  cubic  yard  was 
as  follows : 


Fig.  72.— Concrete  Mixing  Plant  fur  Lock  Wall:?,  Illinois  &  Mississippi  Canal. 

Item.  Per  Cu.  Yd. 

1.45  bbls.  Portland  cement   $4-33° 

0.55  cu.  yd.  crushed  stone 0.604 

0.252  cu.  yd.  pebbles 0.328 

0.465  cu.  yd.  sand 0.419 

40,000  ft.  B.  M.  lumber  (l/4  cost  of  $16  per  M.) 0.348 

Carpenter  work  on  forms  0.780 

Mixing  and  placing  concrete  1.909 

20  per  cent,  cost  of  plaTit 0.090 

Miscellaneous   0.182 

Total    $8.99 

Miring  Plant. — The  concrete  for  all  the  lock  work  of  1893-4 
was  mixed  by  the  plant  shown  by  Figs.  72  and  73.    The  mixer 


LOCKS,   DAMS,    BREAKWATERS. 


199 


plant  proper  consisted  of  a  king  truss  carried  by  two 
A-frames  of  unequal  height ;  under  the  higher  end  of  the  truss 
was  a  frame  carrying  a  4-ft.  cubical  mixer  and  under  the  lower 
end  a  pit  for  a  charging  box  holding  40  cu.  ft.  This  charging 
box  was  hoisted  by  J^-in.  steel  cable  running  through  a  pair 
of  double  blocks  as  shown ;  the  slope  of  the  lower  chord  of  the 
truss  was  such  that  the  cable  hoisted  the  box  and  carried  it 
forward  without  the  use  of  any  latching  devices.  On  two 


Fig.  73.— Stone  Crushing  Plant  for  Lock  Walls,  Illinois  &  Mississippi  Canal. 

sides  of  the  pit  were  tracks  from  the  sand  and  stone  piles  and 
on  the  other  two  sides  were  the  cement  platform  and  water 
tank.  The  charging  box  dumped  into  the  hopper  above  the 
mixer  and  the  mixer  discharged  into  cars  underneath.  A 
I5-HP.  engine  operated  the  hoist  by  one  pulley  and  the  mixer 
by  the  other  pulley.  Nine  revolutions  of  the  mixer  made  a 

r2'**' 


"/W/V"     r     r-\r  -r»-vyv        "/f" 

tf'O' >K~7fc"' 


Section  b-H. 
Fig.    74.— Forms    for    Guard    Lock,    Illinois    &    Mississippi    Canal. 

perfect  mixture.  The  plant  as  illustrated  was  slightly  changed 
as  the  result  of  experience  in  constructing  the  guard  lock. 
The  charging  hopper  was  lowered  6  ins.  and  the  space  between 
the  mixer  and  lower  platform  reduced  by  9  ins.;  diagonal 
braces  were  also  inserted  under  the  timbers  carrying  the  mixer 
axles.  This  plant  cost  for  framing  and  erection  $300  and  for 


200 


CONCRETE    CONSTRUCTION. 


machinery  delivered  $706.  The  crushing  plant  shown  by  Fig. 
73  consisted  of  a  No.  2  Gates  crusher  delivering  to  a  bucket 
elevator. 

Guard  Lock. — The  forms  employed  in  constructing  the 
guard  lock  are  shown  by  Fig.  74,  and  in  this  drawing  the 
trestle  and  platform  for  the  concrete  cars  are  to  be  noted. 
The  walls  were  concreted  in  sections.  A  batch  of  concrete 
consisted  of  I  bbl.  cement,  10  cu.  ft.  sand  and  20  cu.  ft.  crushed 
stone.  The  average  run  per  8-hour  day  was  40  batches  of 
facing  and  60  batches  concrete,  representing  100  bbls.  cement. 
The  gang  worked  was  as  follows : 

Duty.  No.  Men. 

Handling  cement 3 

Filling  and  pushing  sand  car 5 

Filling  and  pushing  stone  car ....'.'.'•     9 

Measuring  water. I 

Dumping  bucket  on  top  platform 3 

Opening  and  closing  door  of  mixer.  ......        i 

Operating  friction  clutch I 

Attending  concrete  cars  under  mixer I 

Dumping  cars  at  forms 2 

Spreading  concrete  in  forms 3 

Tamping  concrete  in  forms. 10 

Mixing   mortar  for  facing 6 

Finishing  top  of  wall 2 

Hauling  concrete  cars  with  i  horse 

Engineman  operating  hoist 

Engineman  operating  engine 

Foreman  in  charge  of  forms 

General  foreman.. 

^    v 

Total 52  100.00 

The  percentages  of  cost  in  this  statement  have  been  calcu- 
lated by  the  authors  upon  the  assumption  that  each  laborer 
received  one-half  as  much  wages  as  each  engineman,  foreman 
and  horse  and  driver  per  8  hours,  which  would  make  the  total 
daily  wages  equivalent  to  the  wages  of  57  men.  Wages  of 
common  labor  were  $1.50  per  day.  Considering  the  size  of  the 
gang  the  output  of  40  batches  of  mortar  and  60  batches  of 
concrete  per  day  was  very  small.  The  total  yardage  of  con- 


LOCKS,  DAMS,   BREAKWATERS. 


2OI 


crete  in  the  guard  lock  was  3,762  cu.  yds.,  2,212  cu.  yds.  in 
the  walls  and  1,550  cu.  yds.  in  foundations,  culverts,  etc.     Its 
cost  per  cubic  yard  was  made  up  as  follows  : 

Item.  Total. 

5,246  bbls.  Portland  cement  ............  $15,604 

152  bbls.  natural  cement  ..............          84 

2,910  cu.  yds.  stone  ...................     2,901 

126  cu.  yds.  pebbles  ..................         113 

1,970  cu.  yds.  sand  ................... 

145,000  ft.  B.  M.  lumber  04th  cost)  .... 

Iron  for  forms,  trestles,  etc 

Coal,  oil,  miscellaneous  ........  ....... 

Carpenter  work  ......................      2,726 

Mixing  and  placing  concrete  ...........     6,693 

Pumping,  engineering,  misc  ...........        742 

20  per  cent,  of  plant  ..................        550 


659 

90 

327 


Per  Cu.  Yd. 

$4.170 

0.771 

0.401 

0.175 

0.024 
0.087 
0.724 
1.780 
0.197 
0.146 


Total    $31,887 


$8.475 


Fig. 


Form  frr  Luck  Wall.  Lock  37. 

75. — Forms    for   Regular   Lock    Walls, 


Illinois   &    Mississippi   Canal. 


Lock  No.  j/. — The  character  of  the  forms  used  in  construct- 
ing the  lock  walls  is  shown  by  Fig.  75.  The  walls  were  built 
in  sections  and  work  was  continuous  with  three  8-hour  shifts 
composed  about  as  specified  for  the  guard  lock  work  except 
that  one  or  twojnen  were  added  in  several  places  making  the 
total  number  58  men.  The  average  output  per  shift  was  65 
batches  of  concrete  and  31  batches  of  facing  mortar.  The  cost 
of  the  work,  comprising  3,767  cu.  yds.,  was  as  follows : 


202  CONCRETE    CONSTRUCTION, 

Item.  Total.          Per  Cu.  Yd. 

4,564  bbls.  Portland  cement $14,181  $3.764 

2,460  cu.  yds.  crushed  stone 4,521  1.200 

250  cu.  yds.  pebbles 325  0.086 

1,750  cu.  yds.  gravel 2,335  0.619 

450  cu.  yds.  sand '.  .        450  0.119 

180,000  ft.  B.  M.  lumber  04th  cost) .  .        990  0.236 

Fuel,  light,  repairs,  etc 1,171  0.31 1 

Carpenter  work 2,526  0.671 

Pumping  270  0.071 

Mixing  and  placing  concrete 6,170  1.632 

20%  cost  of  plant 730  O-I93 


Total    $33,669  $8.902 

Lock  A'o.  $6. — The  forms  used  were  of  the  construction 
shown  by  Fig.  75.  Three  shifts  were  worked,  each  composed 
as  specified  for  the  guard  lock,  except  that  the  number  of 
tampers  and  spreaders  was  doubled,  bringing  the  gang  up  to 
65  men.  The  average  output  per  gang  per  shift  was  76  batches 
of  concrete  and  35  batches  of  facing  mortar.  The  cost  of  2,141 
cu.  yds.  of  concrete  in  this  lock  was  as  follows : 

Item.  Total.  Per  Cu.  Yd. 

3,010  bbls.   Portland  cement $9,057  $4-23 

1,377  cu-  yds.  broken  stone 1,922  0.90 

393  cu.  yds.  pebbles 354  0.17 

459  cu.  yds.  gravel 310  0.15 

500  cu.  yds.  sand 889  0.42 

150,000  ft.  B.  M.  lumber  (J4th  cost) .  .  .        600  0.28 

Fuel,  light,  repairs,  etc 253  0.68 

Carpenter  work 1,472  o.i  I 

Mixing  and  placing  concrete 3*897  1.82 

20%  cost  of  plant 650  0.30 

Total  $19,404  $9.06 

The  preceding  data,  made  public  by  Mr.  Woermann  in  1894, 
are  supplemented  by  the  following  information  prepared  for 
the  authors: 

"If  any  criticism  was  to  be  made  of  the  concrete  masonry 
erected  in  1893  and  1894,  it  would  probably  be  to  the  effect 


LOCKS,  DAMS,   BREAKWATERS.  203 

that  it  was  too  expensive.  The  cost  of  the  masonry  erected 
during  those  two  seasons  was  $8  to  $9  per  cu.  yd.  Our  records 
showed  that  about  45  per  cent,  of  this  cost  was  for  Portland 
cement  alone,  and  moreover,  that  40  per  cent,  of  the  total 
cement  used  at  a  lock  was  placed  in  the  8-in.  facing  and  5-111. 
coping.  So  in  the  seven  locks  erected  in  1895  on  the  eastern 
section,  the  facing  was  reduced  to  3  ins.  and  the  proportions 
changed  from  1-2  to  i-2l/2. 

"In  1898  this  cost  received  another  severe  cut,  and  Major 
Marshall's  instructions  stated  that  the  facing  should  not  ex- 
ceed \l/2  ins.  in  thickness  nor  be  less  than  ^J-in.,  while  the 
layer  of  fine  material  on  top  of  the  coping  was  to  be  only  suffi- 
cient to  cover  the  stone  and  gravel.  The  amount  of  sand 
was  again  increased  so  that  the  proportions  were  1-3. 

"The  cost  of  the  Portland  cement  concrete  was  likewise 
cheapened  by  increasing  the  amount  of  aggregates.  On  the 
earlier  work  the  proportions  were  1-2-2-3,  while  on  the  work 


3*10'! 


Fig.   76.— Sketch   Showing  Method  of  Attaching  Lagging  to  Studs,   Illinois  & 

Mississippi  Canal. 

in  1898  the  proportions  were  1-4-4.  The  cost  of  the  walls  was 
further  cheapened  by  using  Utica  cement  in  the  lower  steps 
of  the  wall,  with  2  ft.  of  Portland  cement  concrete  on  the  face. 
The  proportions  used  in  the  Utica  cement  concrete  were 
I-2V2-2J/2.  This  lower  step  is  one-third  of  the  height,  or 
about  7  ft. 

"The  forms  were  of  the  same  character  as  those  used  on 
the  first  locks,  except  that  for  lining  the  inner  face,  3  x  lo-in. 
hard  pine  planks  were  substituted  for  the  4  x  8-in.  white  pine. 
The  hard  pine  was  damaged  less  by  the  continuous  handling, 
and  the  cost  was  practically  the  same.  There  was  also  an 
important  change  made  in  the  manner  of  fastening  the  plank 
to  the  8x  lo-in.  posts.  A  strip  i^4  i«s.  square  was  thoroughly 
nailed  to  each  post,  once  for  all,  with  2od.  spikes,  arrd  the 
planking  was  then  nailed  from  the  outside,  as  shown  in  Fig.  76. 
This  kept  the  face  of  the  plank  in  a  perfectly  smooth  condition, 
and  prevented  the  formation  of  the  little  knobs  on  the  face  of 


204  CONCRETE    CONSTRUCTION. 

the  concrete  which  represented  all  the  old  nail  holes.  This  style 
of  forming  was  also  easier  to  take  apart  after  the  setting  of  the 
concrete.  Rough  pine  planks,  2xi2-in.,  were  used  for  the 
back  of  the  form,  the  same  as  before. 

"In  order  to  keep  ahead  of  the  concrete  force  it  was  neces- 
sary to  use  two  gangs  of  carpenters,  erecting  the  forms  for 
the  next  two  locks.  Each  gang  consisted  of  about  20  car- 
penters (at  $2.25)  and  10  helpers  (at  $1.50)  ;  but  men  were 
transferred  from  one  to  the  other,  according  to  the  stage  of 
completion  of  the  two  locks.  In  addition  to  these  two  gangs, 
two  carpenters  were  on  duty  with  each  concrete  shift  to  put 
in  the  steps  in  the  back  of  the  forms.  Sufficient  lumber  was 
required  for  the  forms  for  three  complete  locks,  and  14  locks 
(Nos.  8  to  21 )  were  built. 

"The  same  type  of  mixer  has  been  used  as  on  the  earlier 
work  at  Milan,  namely,  a  4-ft.  cubical  steel  box  mounted  on 
corners  diagonally  opposite.  On  account  of  the  greater  num- 
ber of  locks  to  be  built  on  the  eastern  section,  however,  two 
mixers  were  found  necessary,  so  that  while  the  concrete  force 
was  at  work  at  one  lock,  the  carpenters  and  helpers  were  erect- 
ing the  mixer  at  the  next  lock.  The  facing  was  mixed  by  hand. 
After  turning  over  the  dry  cement  and  sand  at  least  twice  with 
shovels,  the  mixture  was  then  cast  through  a  No.  5  sieve,  after 
which  the  water  was  incorporated  slowly  by  the  use  of  a 
sprinkling  can  so  as  to  avoid  washing.  The  secret  of  good 
concrete,  after  the  selection  of  good  materials,  is  thorough 
mixing  and  hard  tamping.  Each  batch  of  concrete,  consisting 
of  about  1.2  cu.  yds.  in  place,  was  turned  in  the  mixer  for  not 
less  than  2  mins.  at  the  rate  of  9  revolutions  per  minute.  The 
amount  of  tamping  is  indicated  by  the  fact  that  about  16  men 
out  of  72  on  each  shift  did  nothing  but  tamp.  The  rammers 
used  were  6  ins.  square  and  weighed  33  Ibs.  The  bottom  of 
the  rammer  consisted  of  three  ridges,  each  i-in.  in  height,  so  as 
to  make  more  bond  between  the  successive  layers. 

"On  the  eastern  section  the  top  of  the  lock  walls  was  higher 
above  the  ground,  as  a  rule,  than  at  the  Milan  locks,  and  the 
cars  were  run  up  an  incline  with  a  small  hoisting  engine.  A 
I5-HP.  portable  engine  and  boiler  operated  the  bucket  hoist 
from  one  pulley,  the  mixer  from  the  other  pulley,  and  also 
furnished  steam  for  the  hoist  which  pulled  the  cars  up  the 


LOCKS,  DAMS,   BREAKWATERS. 


205 


incline.  The  incline  made  an  angle  of  about  30°  with  the 
ground.  The  practice  of  carrying  on  two  sections  at  once  was 
continued  the  same  as  on  the  western  section.  Each  main 
wall  was  systematically  divided  into  n  sections,  making  each 
section  about  20  ft.  long.  The  corners  of  the  coping  were 
dressed  to  a  quadrant  of  about  3  ins.  radius  with  a  round 
trowel  like  those  used  on  cement  walks.  In  fact,  the  whole 
method  of  finishing  the  coping  was  the  same  as  is  used  on 
concrete  walks.  The  mortar  was  put  on  rather  wet  and  then 
allowed  to  stand  for  about  20  mins.  before  finishing.  This 
allowed  the  water  to  come  to  the  surface  and  prevented  the 
formation  of  the  fine  water  cracks  which  are  sometimes  seen" 
on  concrete  work.  After  its  final  set  the  coping  was  covered 
with  several  inches  of  fine  gravel  which  was  kept  wet  for  at 
least  a  week. 

"The  last  concrete  laid  during  the  season  was  in  November, 
on  Lock  No.  21,  and  Aqueducts  Nos.  2  and  3.  Portions  of 
these  structures  were  built  when  the  temperature  was  below 
freezing.  The  water  was  warmed  to  about  60°  or  70°  F., 
by  discharging  exhaust  steam  into  the  tank.  Salt  was  used 
only  in  the  facing,  simply  sufficient  to  make  the  water  taste 
saline.  The  maximum  amount  used  on  the  coldest  night  when 
the  temperature  was  about  20°  F.  was  il/2  per  cent. 

The  concrete  force  on  each  shift  was  as  follows : 

Men. 

Filling   and   pushing  stone   car. 10 

Filling  and  pushing  gravel  car 8 

Measuring  cement 3 

Measuring  water  and  cleaning  bucket 2 

Dumping  bucket  on  top  platform 2 

Operating  mixer  . 2 

Loading  concrete  cars .7"^' 

Pushing  and  dumping  cars  on  forms 3 

Switchmen   on   forms 2 

Spreading  concrete  in  forms 12 

Tamping  concrete  in  forms 16 

Mixing   facing 3 

Water  boys 2 

Total  laborers  .  .  66 


206  CONCRETE    CONSTRUCTION. 

Operating  hoists 2 

Finishing  coping 2 

Fireman I 

Sub-overseers    2 

Overseer i 

Total  force  74 

"The  cost  of  material  and  labor  at  Lock  No.  15  (lo-ft.  lift), 
which  contains  2,559  cti.  yds.  of  concrete,  was  as  follows : 

Materials.  Per  cu.yd. 

0.56  bbl.  Portland  cement  (0.96  per  cu.  yd.) $1.42 

0.64  bbl.  Utica  cement  (1.58  per  cu.  yd.) .30 

0.58  cu.  yd.  stone  ' 1.15 

0.60  cu.  yd.  gravel  .52 

14  ft.  B.  M.  lumber*  at  $15  per  M 21 

0.6  Ib.  spikes .01 

Coal  (10  tens  in  all,  at  $1.70) .01 

0.35  gal.  kerosene .03 


Total    materials $3.65 

Labor. 

Erecting  forms  ($7  per  M.) .45 

Removing  forms  ($2  per  M.) .13 

Erecting  and  removing  mixer  ($161) .06 

Loading  and  unloading  materials  at  yards  and  lock  sites         .23 

Track  laying  ($86) 03 

Train  service  (narrow  gage  road) .09 

Delivering  materials  to  mixer .28 

Mixing  concrete  . . : .11 

Depositing  concrete .21 

Tamping  concrete .21 

Mixing,  depositing  and  tamping,  69  cu.  yds.  face  mor- 
tar ($160)    23 

General  construction  ($553) 22 

Total  labor $2.25 

*The  lumber  was  used  nearly  five  times,    vhich   accounts    for   its   low   cost 
per  cu.  yd. 


LOCKS,   DAMS,   BREAKWATERS.  207 

"There  were  1,430  cu.  yds.  of  Portland  cement  concrete. 
69  cu.  yds.  of  Portland  cement  mortar  facing,  and  1,059  cu- 
yds.  of  Utica  cement  concrete.  The  Portland  concrete 
cost  $6.43  per  cu.  yd. ;  the  Utica  concrete,  $4.77  per  cu.  yd. 
The  following  is  the  cost  of  labor  on  Lock  No.  20  (n-ft.  lift.; 
2,750  cu.  yds.)  : 

Per  cu.  yd. 

Erecting  forms  ($7  per  M.) $  .434 

Removing  forms  ($1.70  per  M.) 113 

Erecting  and  removing  mixer  ($151) .058 

Loading  and  unloading  at  yards,  lock  sites,  etc .614 

Tracks    .024 

Train   service    (narrow   gage) .016 

Pumping    .1 14 

Delivering  material  to  mixer .288 

Mixing  concrete .134 

Depositing  concrete    .205 

Tamping  concrete .192 

Mixing,     depositing     and    tamping,     85     cu.    yds.    face 

mortar    .071 

General  construction .246 

Total    $2.509 

COST  OF  HAND  MIXING  AND  PLACING,  CANAL 
LOCK  FOUNDATION.— Mr.  Geo.  P.  Hawley  gives  the  fol- 
lowing record  of  mixing  and  placing  4,000  cu.  yds.  of  1-4^2 
gravel  concrete  for  the  foundation  of  a  lock  constructed  for 
the  Illinois  and  Mississippi  Canal  in  1897.  The  concrete  was 
mixed  on  I4xi6-ft.  board  platforms,  from  which  it  was  shov- 
eled directly  into  place.  The  materials  were  brought  to  the 
board  in  wheelbarrows.  Two  boards  were  used,  the  usual 
gang  for  each  being  4  men  wheeling  gravel,  4  men  mixing,  I 
man  sprinkling,  2  men  depositing  and  leveling  and  2  men 
tamping.  The  two  gangs  were  worked  against  each  other. 
Ten  hours  constituted  a  day's  work,  and  the  average  time  and 
cost  per  cubic  yard  for  mixing  and  placing  were : 


208  CONCRETE    CONSTRUCTION. 

Cts. 

Foreman,  0.21  hr.,  at  30  cts 6.30 

Laborers,  3.339  hrs.,  at  1 5  cts 50.09 

Pump  runner,  0.129  hr.,  at  20  cts 3.58 

Water  boy,  0.087  nr->  at  71/*  cts 0.65 

Total  labor  per  cu.  yd.,  cents 60.62 

BREAKWATER  AT  MARQUETTE,  MICH.— The  break- 
water extends  out  from  the  shore  and  consists  of  a  prism  of 
concrete  resting  on  timber  cribs  filled  with  stone.  Originally 
the  cribs  carried  a  timber  superstructure ;  this  was  removed 
to  give  place  to  the  concrete  work.  A  typical  cross-section  of 
the  concrete  prism  is  shown  by  Fig.  77;  the  prism  is  23  ft. 


Fig.  77.— Cross  Section  of  Marquette  Breakwater. 

wide  on  the  base.  Farther  in  shore  the  base  width  was  re- 
duced to  20  ft.,  and  in  the  shore  section  the  prism  was  changed 
to  a  triangular  trapezoid  by  continuing  the  first  slope  to  the 
bottom  cutting  off  the  berm  and  second  slope.  The  wooden 
structure  was  removed  to  a  level  i  ft.  below  mean  low  water 
and  on  it  a  concrete  footing  approximately  2  ft',  thick  was  con- 
structed for  the  prism  proper.  This  footing  reached  the  full 
width  of  the  crib  and  was  constructed  in  various  ways  during 
the  5  years  through  which  the.  work  continued.  At  first  the 
footing  concrete  was  deposited  loose  under  water  by  means 
of  bottom  dumping  buckets  ;  later  the  stone  filling  of  the  cribs 
was  simply  leveled  up  by  depositing  concrete  in  bags,  and 
last  toe  and  heel  blocks  were  molded  and  set  flush  with  the 
sides  of  the  crib  and  filled  between.  Methods  of  construction 
and  records  of  cost  are  reported  for  portions  only  of  the  work 
and  these  are  given  here. 

Footing    Placed    under    Water    with    Buckets. — Besides    the 
material  track  which  was  constructed  along  the  old  wooden 


LOCKS,   DAMS,   BREAKWATERS. 


209 


structure  the  plant  consisted  of  a  mixing  scow  and  a  derrick 
scow,  which  were  moored  alongside  the  work.  The  sand,  stone 
and  cement  were  brought  out  in  cars  between  working  hours 
and  stored  on  the  mixing  scow,  enough  for  one  day's  work  at  a 
time.  The  derrick  handled  a  4O-cu.  ft.  bottom  dump  bucket, 
which  sat  in  a  well  on  the  mixing  scow  with  its  top  flush  with 
the  deck.  The  concrete  was  mixed  by  hand  on  the  deck  and 
shoveled  into  the  bucket ;  the  bucket  was  then  handled  by  the 
derrick  to  the  cr;b  and  lowered  and  dumped  under  water.  The 
gang  consisted  of  24  men,  i  foreman,  i  master  laborer,  14  men 
shoveling  and  mixing,  3  men  wheeling  materials,  i  derrick 
man  and  3  men  placing  and  depositing  concrete.  No  record 
of  output  of  this  gang  is  available.  The  cost  of  the  concrete 
in  place  with  wages  $1.25  to  $1.40  per  day  for  common  labor 
is  given  as  follows : 

Materials.  Per  cu.  yd. 

i  .21  bbls.  (459  Ibs.)  cement  at  $2.20 $2.657 

i  cu.  yd.  stone  at  $1.58 1.580 

0.5  cu.  yd.  sand  at  $0.50 0.250 

2.02  Ibs.  burlap  at  $0.037 •     °-°?5 

Twine  and  needles   0.005 

Total   materials    , $4.567 

Labor. 

Loading  scow  with  materials $0.4114 

Mixing  concrete 0.8459 

Depositing  concrete 0.5242 

Total  labor  $1.7815 

Grand  total  $6.348 

These  figures  are  based  on  some  757  cu.  yds.  of  concrete 
footing.  In  explanation  of  the  items  of  burlap,  etc.,  it  should 
be  said  that  the  cribs  were  carpeted  with  burlap  to  prevent 
waste  of  concrete  into  the  stone  fill. 

Leveling  Off  Cribs  unth  Concrete  in  Bags. — The  sketch, 
Fig.  78,  shows  the  method  of  leveling  off  the  cribs  with  con- 
crete in  bags.  The  concrete  was  mixed  by  hand  on  shore,  and 
filled  into  8-oz.  burlap  bags,  6  ft.  long  and  80  ins.  around,  hold- 
ing 2,000  Ibs.  The  bags  were  filled  while  lying  in  position  in  a 
skip  holding  one  bag.  A  skip  was  lifted  by  gallows  frame  and 


2IO 


CONCRETE    CONSTRUCTION. 


tackle  onto  a  car  and  run  out  to  the  work  where  the  derrick 
scow  handled  the  skip  to  the  crib,  lowered  it  into  the  water 
and  dumped  the  bag.  The  cost  of  making  and  placing  some 
375  cu-  yds.  °f  concrete  in  bags  is  given  as  follows : 


Fig.    78.— Cross   Section   of  Marquette  Breakwater  Showing  Manner  of  Con- 
structing Footing  with    Bags  of   Concrete. 

Materials.  Total.  Per  cu.  yd. 

453  bbls.  cement  at  $2.627 $1,190.03  $3-!/3 

375  cu.  yds.  stone  at  $1.619 607.13  1.619 

180  cu.  yds.  sand  at  $0.392 7°-56  0.188 

3,220  yds.  burlap  at  $0.03304 106.39  0-283 

Twine  and  needles 6.36  0.017 

Total   materials    $1,980.47  $5.280 

Labor  Mixing. 

108  hrs.  master  laborer  at  $0.21  Js. .  .  .$      23.42  $0.062 

1,750  hrs.  labor  at  $0.175 306.25  0.816 

Superintendence  12.55  0.033 

Total  labor  mixing $    342.22  $0.91 1 

Labor  transporting. 

306  hrs.  labor  at  $0.175 $      53-55  $0.142 

Superintendence    5.25  0.014 

Totr.l  labor  transporting $      58.80  $0.156 

Labor  Depositing. 

108  hrs.  engineman  at  $0.25 $      27.00  $0.072 

108  hrs.  master  laborer  at  $o.2i",s ....         23.42  0.062 

510  hrs.  labor  at  $0.175 89-25  0.238 

Superintendence    !3-25  °-°35 

Total  labor  depositing $    152.92  $0.407 

Grand  total  labor $    553.94  $M77 

Grand  total  materials  and  labor.  .$2.534.41  $6-757 


LOCKS,   DAMS,   BREAKWATERS. 


211 


Molding  Footing  Blocks. — The  blocks  used  at  the  toe  of  the 
prism  were  of  the  form  and  dimensions  shown  by  Fig.  79. 
They  were  molded  in  a  temporary  shed  heated  to  50°  to  65°  F., 
and  provided  with  a  2  x  8-in.  dressed  plank  floor  on  12  x  12-in. 
sills.  The  floor  formed  the  bottoms  of  the  block  molds.  Four 
molds  were  used,  each  consisting  of  four  sides.  Three  laborers 
molded  one  block,  2.22  cu.  yds.  per  day,  wheeling,  mixing, 
erecting  and  removing  forms,  placing  concrete  and  doing  all 
other  work.  The  cost  of  making  40  blocks  was  recorded  as 
follows : 


—r 


JL 


Fig.   79.— Details  of  Toe  Blocks  for  Footing,  Marquette  Breakwater. 

Materials.                                                   Total.  Per  cu.  yd. 

126  bbls.  cement  at  $2.75 $346.50  $3.893 

88.9  cu.  yds.  screenings  at  $1.10 9779  1.098 

40.1  cu.  yds.  sand  at  $0.45 18.04  0.203 

5  gals,  oil  at  $0.65 3.25  0.036 

Total  materials   $465.58  $5.230 

Labor. 

i,ooo  hrs.  labor  at  $0.125 $125.00  $1.404 

Watchman    29.15  0.327 

Labor  cutting  wood  for  fuel 23.80  0.267 

Superintendence 42.66  0.480 

Total  labor $220.61  $2.478 

Total  labor  and  materials $686.19  $7.708 

Molding  Concrete  Prism  in  Place. — The  concrete  prism  was 
molded  in  alternate  sections  10  ft.  long;  the  form  for  the 
isolated  sections  consisted  of  eight  pieces  so  constructed  that 
when  assembled  in  place  and  secured  with  bolts  and  turn- 
buckles  the  form  was  self-contained  as  to  strength  and  re- 
quired no  outside  support  or  bracing.  The  form  once  in  place. 


212  .CONCRETE    CONSTRUCTION. 

all  that  remained  to  be  done  was  to  fill  it,  the  block  with  the 
gallery  through  it  being  molded  in  one  operation.  The  forms 
for  the  connecting  blocks  consisted  of  two  slope  panels,  a 
panel  for  the  harbor  face  and  the  gallery  form,  the  blocks  pre- 
viously molded  making  the  other  sides  of  the  form.  The  con- 
crete was  mixed  by  hand  on  shore,  conveyed  to  the  work  in  i 
cu.  yd.  cars  and  shoveled  into  the  forms,  where  it  was  rammed 
with  35-lb.  rammers.  The  following  record  covers  1,231  cu. 
yds.  of  concrete  prism.  In  this  concrete  some  214  cu.  yds.  of 
rubble  stone  were  embedded.  The  costs  given  are  as  follows : 

Per 
Materials —  Total,     cu.  yd. 

1,780  bbls.  natural  cement  at  $1.068 $1,901.04     $1.545 

963^/2  cu.  yds.  stone  at  $1.619 !>559-9i       1-267 

53I/>  cu.  yds.  screenings  at  $0.392 20.97       0.017 

485.6  cu.  yds.  sand  at  $0.392 190.36       0.154 

Miscellaneous   materials    78.15       0.063 


Totals   $3750-43  $3-°40 

Labor   Mixing — 

254  hrs.  master  laborer  at  $0.21% .$      55.56  $0.045 

4,470  hrs.  labor  at  $0.175 782.42  0.635 

Superintendence    18.20  0.015 


Total  labor  mixing $  856.18  $0.695 

Labor  Transporting  and  Placing — 

35  days  overseer  at  $2.33  1-3.  . . $  81.67  $0.066 

1,949  hrs.  labor  at  $0.175 342.07  0.277 

Superintendence    34-98  0.028 

Total  labor  transporting  and  placing.  .$    458.72     $0.371 

Grand  total,  labor $1,314.90       1.066 

Total  labor  and  materials $5>°65-33       4.112 

No  charge  is  made  under  materials  for  rubble  stone  as  the 
only  cost  for  this  was  cost  of  handling  and  this  is  included 
in  transporting  and  placing. 

BREAKWATER,  BUFFALO,  N.  Y.— The  following  meth- 
ods and  costs  of  mixing  and  placing  some  2,561  cu.  yds.  of 
concrete  are  given  by  Mr.  Emile  Low,  for  10  parapet  wall  sec- 


LOCKS,  DAMS,  BREAKWATERS. 


213 


tions  and  17  parapet  deck  sections  for  a  breakwater  at  Buf- 
falo, N.  Y. 

The  concrete  used  was  a  I  cement,  i  gravel,  i  sand  grit  and 
4  unscreened  broken  stone.  One  bag  of  cement  was  assumed 
to  measure  0.9  cu.  ft.  The  voids  in  the  sand  grit  and  gravel 
were  27  per  cent,  and  in  the  unscreened  stone  39  per  cent.  The 
hardened  concrete  weighed  152  Ibs.  per  cu.  ft. 

Figure  80  shows  the  arrangement  of  the  mixing  plant.  The 
mixer  was  a  5-ft.  cube  mixer  holding  125  cu.  ft.,  mounted  on  a 
trestle  and  operated  by  a  9xi2-in.  horizontal  engine  taking 
steam  from  a  4x  lo-ft.  locomotive  boiler,  also  supplying  steam 
to  two  derrick  engines.  The  material  scow  contained  two 
pockets  for  sand,  one  for  gravel  and  -one  housed  over  for  ce- 
ment. Two  inside  cement  men  passed  out  the  bags  in  lots  of 
six  to  one  outside  cement  man  who  cut  and  emptied  them  into 
the  charging  bucket.  Three  sand  shovelers  each  loaded  a  3.6 
cu.  ft.  barrow  and  wheeled  them  tandem  to  the  bucket,  and 


Pig.    80.— Sketch    Plan    of   Concrete   Mixing   Plant    for   Buffalo    Breakwater. 

two  gravel  men  each  loaded  a  2.7  cu.  ft.  barrow  and  wheeled 
them  tandem  to  the  bucket.  The  broken  stone  was  loaded 
by  eight  shovelers  into  another  bucket,  also  containing  21.6 
cu.  ft.  The  two  buckets  were  alternately  hoisted  and  emptied 
into  the  mixer  hopper,  there  being  a  dump  man  on  the  mixer 
who  dumped  the  buckets  and  attended  to  the  water  supply. 
A  charger  put  the  mixer  in  operation  and  when  the  charge 
was  mixed  the  car  men  dumped  it  into  a  skip  resting  on  a 


2i4  CONCRETE    CONSTRUCTION. 

small  car  which  was  then  run  out  on  the  track  under  the 
mixer  to  the  derrick  which  handled  the  skip  to  the  work.  Der- 
rick A  handled  the  materials  from  the  scows  and  derrick  B 
handled  the  mixed  concrete.  The  force  on  the  derricks  con- 
sisted of  two  enginemen,  four  tagmen  and  the  fireman. 

The  ten  parapet  wall  sections  containing  841  cu.  yds.  were 
built  in  46  hours,  making  17  batches  of  1.07  cu.  yds.,  or  18.2 
cu.  yds.  placed  per  hour.  The  17  parapet  deck  sections  con- 
taining 1,720  cu.  yds.  were  built  in  88  hours,  making  18.8 
batches  of  1.08  cu.  yds.,  or  19.5  cu.  yds.  placed  per  hour.  For 
thectparapet  deck  work  the  force  was  increased  by  2  men  han- 
dling materials  and  I  man  on  the  mixer.  The  labor  cost  of 
mixing  and  placing  the  concrete  was  as  follows : 

Per  Per 

Loading   Gang —  day.         cu.  yd. 

1  assistant    foreman     $  2.00         $0.01 1 

3  cement  handlers 5.25  0.029 

3  sand   shovelers    5.25  0.029 

2  gravel  shovelers   3.50  0.020 

8  stone  shovelers   14.00  0.076 

i  hooker   on    1.75  o.oio 


Totals    $31.75  $0.175 

MixeV  Gang — 

I   dumpman ."....$  1.75  $0.010 

1  charging  man 1.75  o.oio 

2  car  men 3.50  0.020 

2  enginemen  at  $3.25 6.50  0.035 

4  tagmen    at    $2 8.00  0.044 

i   fireman 2.00  o.oi  i 


Totals    $^3.50  $0.130 

Wall  Gang — 

i   Signalman    $  1.75  $0.010 

i  dumper    1.75  o.oio 

6  shovelers  at  $2   12.00  0.065 

4  rammers    7.00  0.038 

i   foreman    4.00  0.022 

$0.145 
$0.450 


Totals    $26.50 


( irand  totals $81.75 


LOCKS,   DAMS,   BREAKWATERS. 


215 


PIER  CONSTRUCTION,  PORT  COLBORNE,  ONT.— 

In    constructing    the    new    harbor    at    Port    Colborne,    Ont., 
on     Lake  Erie,     the     piers     consisted     of    parallel     rows     of 


\ 

I     ^ 

Z'/W    r&  6.  drtsitd  om  fact 

Elevation. 


Plan. 


Fig.  81.— Concrete  Blocks  for  Pier  at      Fig.    82.— Forms   for    Molding   Blocks. 
Port  Colborne  Harbor.  Port  Colborne  Harbor  Pier. 

timber  cribs  set  the  width  of  the  pier  apart  and 
filled  in  and  between  with  stone  blasted  and  dredged 
from  the  lake  bottom  in  deepening  the  harbor.  The  tops  of 


Fig.   83. — Device   for  Handling  Blocks,   Port  Colborne  Harbor  Pier. 

the  cribs  terminated  below  water  level  and  were  surmounted 
by  concrete  walls  set  on  the  outer  edges.  These  walls  were 
filled  between  with  stone  and  the  top  of  the  filling  was 


216 


CONCRETE    CONSTRUCTION. 


floored  part  way  or  entirely  across,  as  the  case  might  be,  with 
a  thick  concrete  slab.  The  footings  of  the  walls  to  just  above 
the  water  level  were  made  of  concrete  blocks  4^/2  x  4  x  7  ft., 
constructed  as  shown  by  Fig.  81.  The  wall  above  the  footing 
course  and  the  floor  slab  were  of  concrete  molded  in  place. 
The  concrete  work  consisted  of  molding  and  setting  concrete 
blocks  and  of  molding  concrete  wall  and  slab  in  place. 

The  blocks  were  molded  on  shore,  shipped  to  the  work  on 
scows  and  set  in  place  by  a  derrick.  Figure  82  shows  the  con- 
struction of  the  forms  for  molding  the  blocks ;  the  bottom  tie 
rods  passed  through  the  partitions  forming  the  ends  of  the 
molds.  The  sides  were  removed  in  48  hours  and  used  over 
again.  Figure  83  shows  the  hooks  used  for  handling  the 


Mixer   Spout 
Mixer  Stand  on  TracU. 


Fig.  84. — Scow  Plant  for  Mixing  and  Placing  Concrete,  Port  Colborne  Harbor 

Pier. 

molded  blocks.  Considerable  trouble  was  had  in  setting  these 
blocks  level  and  close  jointed,  owing  to  the  difficulty  of  level- 
ing up  the  stone  filling  under  water. 

The  mass  concrete  was  mixed  and  placed  by  the  scow  plant, 
shown  by  Fig.  84.  The  scow  was  loaded  with  sufficient  sand 
and  cement  for  a  day's  work  and  towed  to  and  moored  along- 
side the  pier.  Forms  were  set  for  the  wall  on  top  of  the  block 
footing.  These  forms  were  placed  in  lengths  of  60  to  75  ft. 
of  wall  and  resembled  the  block  forms  with  partitions  omitted. 
The  bottoms  of  the  rear  uprights  were  held  by  being  wedged 
into  the  grooves  in  the  blocks,  and  the  bottoms  of  the  front 
uprights  were  held  by  bolts  resting  on  top  of  the  blocks.  The 


LOCKS,  DAMS,   BREAKWATERS. 


217 


tops  of  the  uprights  were  held  together  across  the  wall  by  tie 
bolts.  The  forms  being  placed,  the  mode  of  proceedure  was 
as  follows : 

The  crusher  fed  directly  into  a  measuring  box.  After  some 
6  ins.  of  stone  had  run  into  the  box  the  door  of  the  crusher 
spout  was  closed.  A  wheelbarrow  load  of  sand  was  spread 
over  the  stone  in  the  box  and  over  this  were  emptied  and 
spread  two  or  three  bags  of  cement.  Another  layer  of  stone 
and  then  of  sand  and  of  cement  were  put  in  and  these  opera- 
tions repeated  until  the  box  was  full.  The  box  was  then 
hoisted  and  dumped  into  the  hopper  of  a  gravity  mixer  of  the 
trough  type  which  ran  along  a  track  on  the  scow  and  fed  di- 
rectly into  the  forms.  The  gang  worked  consisted  of  I  fore- 


MoM  Traveler  Track 


L&como+ive  Crcrne 
t4V" M 


^•;x:V;;*yy>;;\ 
|*^:;//- V';?.V:>; 


$mw-mj 

m^tmtm 


J   U   U 


Fig.    85. — Cross-Section    of    Concrete    Pier,    Superior,    Wis. 

man,  I  derrickman  and  18  common  laborers.  This  gang  placed 
from  65  to  75  cu.  yds.  of  concrete  per  day  at  a  labor  cost  of 
50  cts.  per  cu.  yd. 

CONCRETE  BLOCK  PIER,  SUPERIOR  ENTRY,  WIS. 
— The  methods  and  cost  of  constructing  a  concrete  pier  3,023 
ft.  long  and  of  the  cross-section  shown  by  Fig.  85  at  Superior 
entry,  Wisconsin,  are  given  in  the  following  paragraphs. 

Molds  and  Molding. — About  80  per  cent,  of  the  concrete  was 
deposited  in  molds  under  water,  according  to  a  plan  devised 
by  Major  D.  D.  Galliard,  corps  of  engineers.  In  brief  the  con- 
crete was  built  in  place  in  two  tiers  of  blocks,  the  lower  tier 
resting  directly  on  piles  and  being  entirely  under  water  and 


218 


CONCRETE    CONSTRUCTION, 


the  upper  tier  being  almost  entirely  alcove  water.  As  shown 
by  Fig.  85,  a  pile  trestle  was  built  on  each  side  of  the  proposed 
pier  and  a  traveler  for  raising  and  lowering  the  molds  spanned 
the  space  between  trestles. 

The  molds  were  bottomless  boxes  built  in  four  pieces,  two 
sides  and  two  ends,  held  together  by  tie  rods.  Fig.  86  shows 
an  end  and  a  side  of  one  of  the  shallow  water  molds  and  Fig. 
87  shows  in  detail  the  method  of  fastening  the  end  to  the  side. 
It  will  be  seen  that  the  1)4 -in.  turnbuckle  rods  pass  through 
the  ends  of  beams  that  bear  against  the  outside  of  the  mold. 
These  tie  rods  have  eyes  at  each  end  in  which  rods  with 
wedge-shaped  ends  are  inserted.  The  molds  were  erected  on 
the  trestle  by  a  locomotive  crane  and  were  then  lifted  by  the 
mold  traveler,  carried  and  lowered  into  place.  The  largest 
one  of  these  molds  with  its  iron  ballast,  weighed  40  tons.  To 


Fig.   86.— Mold    for   Concrete  Block  for   Pier   at  Superior,   Wis. 

remove  a  mold,  after  the  block  had  hardened,  the  nuts  on  the 
wedge-ended  rods  were  turned,  thus  pulling  the  wedge  end 
from  the  eye  of  the  tie  rod  and  releasing  the  sides  of  the  mold 
from  the  ends.  The  locomotive  crane  then  raised  the  ends  and 
sides,  one  at  a  time,  and  assembled  them  ready  to  be  lowered 
again  for  the  next  block.  The  time  required  to  remove  one  of 
these  4O-ton  molds,  reassemble  and  set  it  again  rarely  ex- 
ceeded 60  minutes  and  was  sometimes  reduced  to  45  minutes. 
The  concrete  was  deposited  in  alternate  blocks  and  the 
molds  described  were  for  the  first  blocks ;  for  the  intermediate 
blocks  molds  of  two  side  pieces  alone  were  used,  the  blocks 
already  in  place  serving  in  lieu  of  end  pieces.  The  two  side 
pieces  were  bolted  together  with  three  tie  rods  at  each  end; 
the  tie  rods  were  encased  in  a  box  of  i-in.  boards  4x4  ins.  in- 


LOCKS,  DAMS,   BREAKWATERS. 


219 


side  which  served  as  a  strut  to  prevent  the  sides  from  closing 
together  and  as  a  means  of  permitting  the  tie  rods  to  be  re- 
moved after  the  concrete  had  set.  The  mold  was  knocked 
down  just  as  was  the  full  mold  described  above  and  .the  boxes 
encasing  the  tie  rods  were  left  in  the  concrete. 


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Fig.    87.— Device    for   Locking   End    and    Side   of    Mold    for   Concrete    Blocks 
for  Pier  at  Superior,   Wis. 

An  important  feature  was  the  device  for  handling  the  molds ; 
this,  as  before  stated,  was  a  traveler,  which  straddled  the  pier 
site,  it  having  a  gage  of  31  ft.  It  carried  a  four-drum  engine, 
the  drums  of  which  were  actuated,  either  separately  or  togeth- 
er, by  a  worm  gear  so  as  to  operate  positively  in  lowering  as 
well  as  in  raising.  The  load  was  hung  from  four  hooks,  de- 


220 


'    CONCRETE    CONSTRUCTION. 


pending  by  double  blocks  and  ^-in.  wire  rope  from  four  trol- 
leys suspended  from  the  trusses  of  the  traveler  ;  this  arrange- 
ment allowed  a  lateral  adjustment  of  the  mold.  The  hoisting 
speed  was  6  ft.  per  minute  and  the  traveling  speed  100  ft.  per 
minute.  The  locomotive  crane  also  deserves  mention  because 
it  was  mounted  on  a  gantry  high  enough  to  permit  material 
cars  to  pass  under  it  on  the  same  trestle,  thus  making  it  prac- 
ticable to  work  two  cranes. 


J 


Side  of  Bucket- 
with  Leaf  Hanging  Down. 


Side   of  Bucket. 

Fig.  88.— Bucket   for  Depositing   Concrete   Under   Water  for  Pier   at 
Superior,    Wis. 

The  concrete  was  received  from  the  mixer  into  drop  bot- 
tom buckets  of  the  form  shown  by  Fig.  88.  The  buckets  were 
taken  to  the  work  four  at  once  on  cais,  and  there  lifted  by  the 
locomotive  crane  and  lowered  into  the  mold  where  they  were 
dumped  by  tripping  a  latch  connected  DV  rope  to  the  crane. 
To  prevent  the  concrete  from  washing,  the  open  tops  of  the 


LOCKS,  DAMS,   BREAKWATERS.  221 

buckets  were  covered  with  3x4  ft.  pieces  of  12-oz.  canvas 
in  which  were  quilted  no  pieces  of  i-i6xix3-in  sheets  of 
lead.  Two  covers  were  used  on  each  bucket  and  were  attached 
one  to  each  side  of  the  bucket  top  so  as  to  fold  over  the  top 
with  a  lap.  This  arrangement  was  entirely  successful  for  its 
purpose. 

Concrete  Mixing. — The  proportions  of  the  subaqueous  con- 
crete were  1-2*^-5  by  volume,  or  1-2.73-5.78  by  weight,  ce- 
ment being  assumed  to  weigh  100  Ibs.  per  cu.  ft. ;  the  propor- 
tions of  the  superaqueous  concrete  were  1-3.12-6.25  by  volume, 
or  1-3.41-7.22  by  weight.  The  dry  sand  weighed  109.2  Ibs.  per 
cu.  ft.,  the  voids  being  35.1  per  cent.;  the  pebbles  weighed 
115.5  Ibs.  per  cu.  ft.,  the  voids  being  31  per  cent. 

The  pebbles  for  the  concrete  were  delivered  by  contract  and 
were  unloaded  from  scows  by  clam-shell  bucket  into  a  hop- 
per. This  hopper  fed  onto  an  endless  belt  conveyor  which  de- 
livered the  pebbles  to  a  rotary  screen.  Inside  this  screen  water 
was  discharged  under  a  pressure  of  60  Ibs.  per  sq.  in.  from  a 
4-in.  pipe  to  wash  the  pebbles.  From  the  screen  the  pebbles 
passed  through  a  chute  into  4-cu.  yd  cars  which  were  hauled 
up  an  incline  to  a  height  of  65  ft.  by  means  of  a  hoisting  en- 
gine. The  cars  were  dumped  automatically,  forming  a  stock 
pile.  Under  the  stock  pile  was  a  double  gallery  or  tunnel 
provided  with  eight  chutes  through  the  roof  and  from  these 
chutes  the  cars  were  loaded  and  hauled  by  a  hoisting  engine 
up  an  inclined  trestle  to  the  bins  above  the  concrete  mixer. 
The  sand  was  handled  from  the  stock  pile  in  the  same  man- 
ner. The  cement  was  loaded  in  bags  on  a  car  in  the  ware- 
house, hauled  to  the  mixer  and  elevated  by  a  sprocket  chain 
elevator. 

Chutes  from  the  bins  delivered  the  materials  into  the  con- 
crete mixer,  which  was  of  the  Chicago  Improved  Cube  type, 
revolving  on  trunnions  about  an  axial  line  through  diagonal 
corners  of  the  cube.  The  mixer  possessed  the  advantage  of 
charging  and  discharging  without  stopping.  It  was  driven  by 
a  7  x  lo-in.  vertical  engine  with  boiler.  The  mixer  demon- 
strated its  ability  to  turn  out  a  batch  of  perfectly  mixed  con- 
crete every  I  1-3  minutes.  It  discharged  into  a  hopper  pro- 
vided with  a  cut-off  chute  which  discharged  into  the  concrete 
buckets  on  the  cars. 


222  CONCRETE    CONSTRUCTION. 

Labor  Force  and  Costs. — In  the  operation  of  the  plant  55 
men  were  employed,  43  being  engaged  on  actual  concrete  work 
and  12  building  molds  and  appliances  for  future  work.  The 
work  was  done  by  day  labor  for  the  government  and  the  cost 
of  operation  was  as  follows  for  one  typical  week,  when  in  six 
days  of  eight  hours  each,  the  output  was  1,383  cu.  yds.,  or  an 
average  of  230  cu.  yds.  per  day.  The  output  on  one  day  was 
considerably  below  the  average  on  account  of  an  accident  to 

the  plant,  but  this  may  be  considered  as  typical. 

» 

Pebbles  from  Stock  Pile  to  Mixer —  Per  cu.  yd. 

4  laborers  at  $2 $0.0348 

i   engineman  at  $3   0.0131 

Coal,  oil  and  waste  at  $1.03 0.0043 

Sand  from  Stock  Pile  to  Mixer — 

5  laborers  at  $2  , $0.0434 

i   engineman   at  $2.50 0.0109 

Coal,  oil  and  waste  at  $0.82  . 0.0035 

Cement  from  Warehouse  to  Mixer — 
5  laborers   at   $2    $0.0434 

Mixing  Concrete — 

i  engineman  at  $2.50 $0.0109 

i  mechanic  at  $2.50  ' 0.0108 

Coal,  oil  and  waste  at  $1.29 0.0056 

Transporting  Concrete — 

4  laborers  at  $2 $0.0348 

i  engineman  at  $3    0.0130 

Coal,  oil  and  waste  at  $0.66 0.0028 

Depositing  Concrete  in  Molds — 

4  laborers   at  $2    $0.0348 

i   engineman  at  $3   0.0130 

i   rigger  at  $3    0.0130 

Coal,  oil  and  waste  at  $1.18 0.0051 

Assembling,  Transporting,  Setting  and  Removing  Molds — 

4  laborers  at  $2 $0.0347 

I  engineman  at  $3.25 0.0141 

I  carpenter  at  $3 0.0130 

I  mechanic  at  $2.50  0.0109 

Coal,  oil  and  waste  at  $1.39 0.0060 


LOCKS,  DAMS,   BREAKWATERS. 


223 


Care  of  Tracks — 

I  laborer  at  $2 , ;  =. , $0.0086 

I  mechanic   at   $2.50    ..............................   0.0109 

Supplying  Coal — 
3  laborers   at  $2    ..,.,..,,.. .................  $0.0260 

Blacksmith  Work— 

i  laborer  at  $2 $0.0086 

I  blacksmith  at  $3.25 , . .  . 0.0141 

I  waterboy  at  $0.75 0.0032 


Total  per  cubic  yard   «..•,.,...,,-.. $0.4473 

Add  75%  of  cost  of  administration 0.1388 


Total  labor  per  cu.  yd. $0.5861 

The  total  cost  of  each  cubic  yard  of  concrete  in  place  was 
estimated  to  be  as  follows: 

Per  cu.  yd. 

Ten-elevenths  cu.  yd.  pebbles  at  $1.085.  •  < $0.9864 

Ten-twenty  seconds  cu.  yd.  sand  at  $0.00 o.oooo 

I  26  bbls.  cement  at  $1.77 2.2302 

Labor  as  above  given   , 0.5861 

Cost  of  plant  distributed  over  total  yardage 0.8400 

Total $4.6427 

It  will  be  noted  that  the  sand  cost  nothing  as  it  was  dredged 
from  the  trench  in  which  the  pier  was  built,  and  paid  for  as 
dredging.  The  cost  of  the  plant  is  distributed  over  this  south 
pier  and  over  the  proposed  north  pier  work  on  the  basis  of 
only  20  per  cent,  salvage  value  after  the  completion  of  both 
piers.  It  is  said,  however,  that  80  per  cent,  is  too  high  an 
allowance  for  the  probable  depreciation. 

DAM,  RICHMOND,  INDIANA.— The  dam  shown  in 
cross-section  in  Fig.  89  was  built  at  Richmond,  Ind. 
It  was  1 20  ft.  long  and  was  built  between  the  abutments  of 
a  dismantled  bridge.  The  concrete  was  made  in  the  propor- 
tion of  i  bbl.  Portland  cement  to  i  cu.  yd.  of  gravel ;  old  iron 
was  used  for  reinforcement.  The  foundations  were  put  down 
by  means  of  a  cofferdam  which  was  kept  dry  by  pumping.  On 
completion  it  was  found  that  there  was  a  tendency  to  scour 
in  front  of  the  apron  and  accordingly  piling  was  driven  and 


224 


CONCRETE    CONSTRUCTION. 


the  intervening  space  rip-rapped  with  large  stone.  Labor  was 
paid  as  follows  per  day:  Foreman,  $3;  carpenter,  $2.50;  ce- 
ment finisher,  $2;  laborers,  $1.50.  The  concrete  was  mixed  by 
hand  and  wheeled  to  place  in  wheelbarrows.  The  cost  of  the 
work  was  as  follows : 


Low  Water 


Fig.   89. — Concrete  Dam  at   Richmond,   Ind. 

Materials —  Per  cu.  yd. 

204  bbls.  cement  at  $1.60 .:.... $1485 

Sand  and  gravel   , 0.800 

Lumber    , 0.610 

Tools,   hardware,    etc    0.445 

Total   materials    $3-34 

Labor — 

Clearing  and  excavating $0.96 

Setting  forms  and  mixing  concrete i.oi 

Pumping    0.27 


Total  labor   $2.24 

Total  materials  and  labor $5-58 

DAM  AT  ROCK  ISLAND  ARSENAL,  ILLINOIS.— The 

dam  was  in  the  shape  of  an  L  with  one  side  192  ft.  and  the 
other  side  208  ft.  long;  it  consists  of  a  wall  30^  ft.  high,  3^ 
ft.  wide  at  the  top  and  6^  ft.  wide  at  the  bottom  with  a  coun- 
terfort every  16  ft.,  26  in  all.  Each  counterfort  extended  back 
16  ft.  and  was  4  ft.  thick  for  a  height  of  6  ft.  and  then  3  ft. 
thick.  There  were  3,500  cu.  yds.  of  concrete  in  the  work, 
which  was  done  by  day  labor  under  the  direction  of  the  U.  S. 
Engineer  in  charge. 


LOCKS,   DAMS,   BREAKWATERS.  22$ 

The  forms  consisted  of  front  and  back  uprights  of  8x  ro-iii. 
stuff  24  ft.  high,  connected  through  the  wall  by  ^4-in.  rods 
which  were  left  in  the  concrete.  The  lagging  was  2xi2-in. 
plank  dressed  down  1^4  ms-  placed  inside  the  uprights.  These- 
forms  were  built  full  height  in  i6-ft.  sections  with  a  counter- 
fort coming  at  the  center  of  each  section.  Each  section  con- 
tained 95  cu.  yds.  of  concrete  and  was  filled  in  a  day's  work. 
The  concrete  was  a  1-4-7  mixture  wet  enough  to  quake  when 
rammed.  Run  of  crusher  limestone  was  used  of  which  50  per 
cent,  passed  a  i-in.  sieve,  17  per  cent  a  No.  3  sieve  and  9  per 
cent,  a  No.  8  sieve.  The  concrete  was  mixed  in  Cockburn  Bar- 
row &  Machine  Co.'s  screw-feed  mixer  which  discharged  into 
2-in.  plank  skips  2  ft.  wide  5  1-3  ft.  long  and  14  ins.  deep,  hold- 
ing l/4  cu.  yd.  These  skips  were  taken  on  cars  to  a  derrick 
crane  overhanging  the  forms  and  by  it  hoisted  and  dumped 
into  the  forms.  The  derrick  was  moved  along  a  track  at  the 
foot  of  the  wall  as  the  work  progressed.  The  concrete  was 
spread  and  rammed  in  6-in.  layers.  The  men  were  paid  $1.50 
per  8-hour's  work  and  the  work  cost  including  footing,  as  fol- 
lows: 

Item—  Total.       Per  cu.  yd. 

Cement    $1,500.00  $0.429 

Sand    400.00  0.114 

Storing  and  hauling  cement 460.00  0.131 

Taking  sand  from  barge  to  mixer 96.00  0.027 

Crushing  stone 1,450.00  0.414 

Mixing  concrete 4,825.00  1.378 

Placing  concrete   1,670.00  0.477 

Lumber  for  forms,  etc 600.00  0.171 

Erecting  and  taking  down  forms 2,450.00  0.700 


Totals  $13,451.00  $3.841 

DAM  AT  McCALL  FERRY,  PA.— The  dam  was  2.700  ft. 
long  and  48  ft.  high  of  the  cross-section  shown  by  Fig.  90  and 
with  its  subsidiary  works  required  some  350,000  cu.  yds.  of 
concrete.  The  plant  for  mixing  and  placing  the  concrete  was 
notable  chiefly  for  its  size  and  cost.  Parallel  to  the  dam, 
which  extended  straight  across  the  river,  and  just  below  its 
toe  a  service  bridge  consisting  of  a  series  of  4O-ft.  concrete 


226 


CONCRETE    CONSTRUCTION. 


arch  spans  was  built  across  the  river.  This  service  bridge  was 
50  ft.  wide  and  carried  four  standard  gage  railway  tracks  be- 
sides a  traveling  crane  track  of  44  ft.  gage.  This  very  heavy 
construction  of  a  temporary  structure  was  necessitated  by  the 
frequency  of  floods  against  which  only  a  solid  bridge  could 
stand ;  it  was  considered  cheaper  in  the  long  run  to  provide  a 
bridge  which  would  certainly  last  through  the  work  than  to 
chance  a  structure  of  less  cost  which  would  certainly  go  out 
with  the  floods.  The  concrete  service  bridge  was  designed  to 


Side         Elevo-Hon  . 

Fig.   90. — Steel  Forms   for  McCall   Ferry  Dam. 

be  destroyed  by  blasting  when-  the  dam  had  been  completed. 
The  method  of  construction  was  to  build  the  dam  in  alternate 
40  ft.  sections,  mixing  the  concrete  on  shore,  taking  it  out 
along  the  service  bridge  in  buckets  on  cars  and  handling  the 
buckets  from  cars  to  forms  by  traveling  cranes. 

The  concrete  mixing  plant  is  shown  by  Fig.  91.  Cars  loaded 
with  cement,  sand  and  stone  were  brought  in  over  the  tracks 
carried  on  the  wall  tops  of  the  bins  and  were  unloaded  re- 


LOCKS,  DAMS,   BREAKWATERS. 


227 


spectively  into  bins  A,  B  and  C,  of  which  there  were  eight 
sets.  Each  set  supplied  material  by  means  of  measuring  cars 
to  a  i  cu.  yd.  Smith  mixer.  Two  sets  of  cars  were  used  for 
each  mixer  so  that  one  could  be  loading  while  the  other  was 
charging.  The  mixers  discharged  into  I  cu.  yd.  buckets  set 
two  on  a  car  and  eight  cars  were  hauled  to  the  work  in  train 
by  an  i8-ton  "dinky."  At  the  work  the  buckets  were  picked 
up  by  the  traveling  cranes  and  the  concrete  dumped  into  the 


Fig.   91. — Concrete  Mixing  Plant  for  McCall  Ferry   Dam. 

forms.  Figure  90  shows  the  construction  of  the  steel  forms. 
Six  sets  of  forms  were  used.  Each  set  consisted  of  five  frames 
spaced  10  ft.  apart  and  braced  together  in  the  planes  parallel 
to  the  dam,  and  each  set  molded  40  ft.  of  dam.  The  lagging 
consisted  of  wooden  boxes  8y2  ft.  wide  and  10  ft.  long.  For 
the  vertical  face  of  the  dam  these  boxes  were  attached  by  bolts 
to  the  vertical  post,  for  the  curved  face  they  were  bolted  to  a 
channel  bent  to  the  curve  and  held  by  struts  from  the  inclined 
post  of  the  steel  frame. 

In  construction  the  footing  and  the  body  of  the  dam  to  an 
elevation  of  5  ft.  above  the  beginning  of  the  curve  were  built 


228 


CONCRETE    CONSTRUCTION. 


continuously  across  the  river;  above  this  elevation  the  dam 
was  built  in  alternate  4O-ft.  sections.  The  strut  back  to  the 
service  bridge  shown  in  the  lower  right  hand  corner  of  Fig. 
90,  shows  the  manner  of  bracing  the  first  3O-ft.  section  of  the 
inclined  post  to  hold  the  lagging  for  the  continuous  portion. 
The  lagging  was  added  a  piece  at  a  time  as  concreting 
progressed.  The  ends  of  each  set  of  frames  for  a  4O-ft.  sec- 
tion were  for  the  isolated  sections  closed  by  timber  bulkheads 
carrying  box  forms  to  mold  grooves  into  which  the  concrete  of. 
the  intermediate  sections  would  bond. 


Charaina  Platform 


?.*6'    £' Floor 


12x12          Drake  Mixei\\ 


End  Elevation. 

Tig.  92.— Traveler  for  Concreting  Dam,  Chaudiere  Falls,  Quebec. 

The  concrete  used  was  a  1-3-5  mixture,  the  stone  ranging  in 
size  from  2  to  5  ins.  Rubble  stone  from  one  man  size  to  l/2 
ton  were  bedded  in  the  concrete.  The  capacity  of  the  con- 
crete plant  was  2,000  cu.  yds.  per  day  or  about  250  cu.  yds.  per 
mixer  per  lo-hour  day. 

DAM,  CHAUDIERE  FALLS,  QUEBEC.— The  dam  was 
800  ft.  long  and  from  16  to  20  ft.  high,  constructed  of  1-2-4 
concrete  with  rubble  stone  embedded.  The  rubble  stones  were 
separated  at  least  9  ins.  horizontally  and  12  ins.  vertically  and 
were  kept  20  ins.  from  faces.  At  one  point  the  rubble 
amounted  to  40  per  cent,  of  the  volume,  but  the  average  for 
the  dam  was  25  to  30  per  cent.  The  stone  was  broken  at 


LOCKS,   DAMS,   BREAKWATERS.  22$ 

the  work,  some  by  hand,  but  most  by  machine,  all  to  pass  a 
2-in.  ring.  Hand-broken  stone  ran  very  uniform  in  size  and 
high  in  voids,  often  up  to  50  per  cent.  Stone  broken  by  crusher 
with  jaws  2  ins.  apart  would  run  20  to  30  per  cent,  over  2  ins. 
in  size  and  give  about  45  per  cent,  voids ;  with  crusher  jaws 
\}/2  ins.  apart  from  98  to  100  per  cent,  was  under  2  ins.  in  size 
and  contained  about  42  per  cent,  of  voids.  It  was  found  that 
if  the  crushers  were  kept  full  all  the  time  the  product  was 
much  smaller,  particularly  with  Gates  gyratory  crusher, 
though  a  little  more  than  rated  power  was  required  when  the 
crusher  was  thus  kept  full.  This  practice  secured  increased 
economy  in  both  quantity  and  quality  of  product.  The  con- 
crete was  made  and  placed  by'  means  of  a  movable  traveler 
shown  by  Fig.  92.  Concrete  materials  were  supplied  to  the 
charging  platform  of  the  traveler  by  means  of  a  traveling  der- 
rick moving  on  a  parallel  track.  In  placing  the  concrete  on 
the  rock  bottom  it  was  found  necessary  in,order  to  secure 
good  bond  to  scrub  the  rock  with  water  and  brooms  and  cover 
it  with  a  bed  of  2  ins.  of  1-2  mortar.  The  method  of  concret- 
ing in  freezing  weather  is  described  in  Chapter  VII. 


CHAPTER  XII. 

METHODS  AND  COST  OF  CONSTRUCTING  BRIDGE 
PIERS  AND  ABUTMENTS. 

The  construction  of  piers  and  abutments  for  bridges  is  best 
explained  by  describing  individual  examples  of  such  work.  So 
far,  in  America,  bridge  piers  have  been  nearly  always  of  plain 
concrete  and  of  form  and  section  differing  little  from  masonry 
piers;  where  reinforcement  has  been  used  at  all  it  has  con- 
sisted of  a  surface  network  of  bars  introduced  chiefly  to  'ensure 
monolithic  action  of  the  pier  under  lateral  stresses.  In  Europe 
cellular  piers  of  reinforced  concrete  have  been  much  used. 
Plain  concrete  abutments  differ  little  in  form  and  volume  from 
masonry  abutments.  Reinforced  concrete  abutments  are  usual- 
ly of  L-section  with  counterforts  bracing  the  upright  slab 
and  bridge  seat  to  the  base  slab. 

Form  work  for  reinforced  abutments  is  somewhat  complex ; 
that  for  plain  abutments  and  piers  is  of  simple  character,  the 
only  variations  from  plain  stud  and  sheathing  construction  be- 
ing in  the  forms  for  moldings  and  coping  and  for  cut-waters. 
For  piers  of  moderate  height  the  form  is  commonly  framed 
complete  for  the  whole  pier,  but  for  high  piers  it  is  built  up 
as  the  work  progresses  by  removing  the  bottom  boards  and 
placing  them  at  the  top.  Opposite  forms  are  held  together 
by  wire  ties  through  the  concrete.  Movable  panel  forms  have 
been  successfully  employed,  but  they  rarely  cheapen  the  cost 
much.  Sectional  forms,  which  can  be  shifted  from  pier  to  pier 
where  a  number  of  piers  of  identical  size  are  to  be  built,  may 
frequently  be  used  to  advantage.  An  example  of  such  use  is 
given  in  this  chapter. 

Derricks  are  the  recognized  appliances  for  hoisting  and  plac- 
ing the  concrete  in  pier  work;  they  are  the  only  practicable 
appliance  where  the  pier  is  high  and  particularly  where  it 
stands  in  water  and  mixing  barges  are  employed.  For  abut- 
ment work  and  land  piers  of  moderate  height  derricks  and 

230 


BRIDGE   PIERS  AND   ABUTMENTS. 


23I 


wheelbarrow  or  cart  inclines  are  both  available  and  where 
much  shifting  of  the  derricks  is  involved  the  apparently  more 
crude  method  compares  favorably  in  cost. 

The  methods  of  placing  concrete  under  water  for  pier 
foundations  are  described  in  Chapter  V,  and  the  use  of 
rubble  concrete  for  pier  construction  is  illustrated  by  several 
examples  in  Chapter  VI.  The  following  examples  of  pier  and 
abutment  construction  cover  both  large  and  small  work  and 
give  a  clear  idea  "of  current  practice. 

COST  OF  CONSTRUCTING  RECTANGULAR  PIER 
FOR  A  RAILWAY  BRIDGE.— This  pier,  Fig.  93,  was  built 
in  water  averaging  5  ft.  deep.  The  cofferdam  consisted  of 


Fig.    93. — Pier  and   Cofferdam  for  a   Railway  Bridge. 

triple-lap  sheet  piling,  of  the  Wakefield  pattern,  the  planks 
being  2  ins.  thick,  and  spiked  together  so  as  to  give  a  coffer- 
dam wall  6  ins  thick.  The  cofferdam  enclosed  an  area  14  x  20 
ft.,  giving  a  clearance  of  I  ft.  all  around  the  base  of  the  con- 
crete pier,  and  a  clearance  of  2  ft.  between  the  cofferdam  and 
the  outer  edge  of  the  nearest  pile.  The  cofferdam  sheet  piles 
were  18  ft.  long,  driven  n  ft.  deep  into  sand,  and  projecting  2 
ft.  above  the  surface  of  the  water. 


232 


CONCRETE    CONSTRUCTION. 


The  concrete  base  resting  on  the  foundation  piles  was  12  x 
18  ft.  The  concrete  pier  resting  on  this  base  was  7x  13  ft.  at 
the  bottom,  and  5x11  ft.  at  the  top.  The  pier  supported  deck 
plate  girders.  There  were  100  cu.  yds.  of  concrete  in  the  pier 
and  base. 

The  cost  of  this  pier,  which  is  typical  of  a  large  class  of  con- 
crete pier  work,  has  been  obtained  in  such  detail  that  we 
analyze  it  in  detail,  giving  the  costs  of  cofferdam  construc- 
tion and  excavation  as  well  as  of  mixing  and  placing  the  con- 
crete. 

Setting  up  and  taking  down  derrick  and  platform: 

4  days  foreman  at  $5.00  $  20.00 

Y±  days  engineman  at  $3.00 2.25 

24  days  blacksmith  at  $3.00 2.25 

24  days  blacksmith  helper  at  $2.00   1.50 

22  days  laborers  at  $2.00 44.00 

Total    , , . . , $  70.00 

Cofferdam — 

7  days  foreman  at  $5.00 , $  35.00 

4  days  engineman  at  $3.00 12.00 

38  days  laborers  at  $2.00   76.00 

I  ton  coal  at  $3.00 3.00 

Total  labor  on  7,900  ft.  B.  M.  at  $16.00 $126.00 

7,900  ft.  B.  M.  at  $20.00 158.00 


Total  for  58  cu.  yds.  excavation .$284.00 

Wet  Excavation — 

1.8  days  foreman  at  $5.00 „. $     9.00 

1.5  days  engineman  at  $3.00 4.50 

9  days  laborers  at  $2.00  18.00 

y*  ton  coal  at  $3.00 1.50 

Total  labor  on  58  cu.  yds.  at  57c $  33.00 

Foundation  Piles — 

960  lin.  ft.  at  ice $  96.00 

4  days  setting  up  driver  and  driving  24  piles  at  $20  per 

day  for  labor  and  fuel  80.00 


Total    . . ., $176.00 


BRIDGE   PIERS  AND   ABUTMENTS. 


233 


Concrete — 

100  cti  yds.  stone  at  $1.00. $100.00 

40  cu.  yds.  sand  at  $0.50   20.00 

100  bbls.  cement  at  $2.00 200.00 

5  days  foreman  at  $5.00 25.00 

50  days  laborers  at  $2.00 100.00 

5  days  engineman  at  $3.00   15.00 

2  tons  coal  at  $3.00 6.00 


Total,  100  cu.  yds.  at  $4.66 $466.00 

8  days  carpenters  at  $3.00 24.00 

2,400  ft.  B.  M.  2-in.  plank  at  $25.00 60.00 

1,000  ft.  B.  M.  4  x  6-in.  studs  at  $20.00 20.00 

Nails,  wire,  etc. 2.00 

Total  forms  for  100  cu.  yds.  at  $1.06 $106.00 

Summary- 
Setting  up  derrick,  etc $  70.00 

Cofferdam  (7,900  ft.  B.  M.) 284.00 

Wet  excavation  (58  cu.  yds.) 33.00 

Foundation  piles   (24) 176.00 

Concrete   (100  cu.  yds.)    466.00 

Forms  (3,400  ft.  B.  M.)   106.00 


Total    $1,135.00 

Transporting  plant    20.00 

20  days  rental  of  plant  at  $5.00 100.00 


Total  cost  of  pier $1,252.00 

Regarding  the  item  of  plant  rental,  it  should  be  said  that  the 
plant  consisted  of  a  pile  driver,  a  derrick,  a  hoisting  engine, 
and  sundry  timbers  for  platforms.  There  was  no  concrete 
mixer.  Hence  an  allowance  $5  per  day  for  use  of  plant  is 
sufficient. 

It  will  be  noted  that  no  salvage  has  been  allowed  on  the 
lumber  for  forms.  As  a  matter  of  fact,  all  this  lumber  was 
recovered,  and  was  used  again  in  similar  work. 

Referring  to  the  cost  of  cofferdam  work,  we  see  that,  in  or- 
der to  excavate  the  58  cu.  yds.  inside  the  cofferdam,  it  was 
necessary  to  spend  $284,  or  nearly  $5  per  cu.  yd.  before  the 
actual  excavation  was  begun.  The  work  of  excavating  cost 
only  57  cts.  per  cu.  yd.,  but  this  does  not  include  the  cost  of 


234  CONCRETE    CONSTRUCTION. 

erecting  the  derrick  which  was  used  in  raising  the  loaded 
buckets  of  earth,  as  well  as  in  subsequently  placing  the  con- 
crete. The  sheet  piles  were  not  pulled,  in  this  instance,  but 
a  contractor  who  understands  the  art  of  pile  pulling  would 
certainly  not  leave  the  piles  in  the  ground.  A  hand  pump 
served  to  keep  the  cofferdam  dry  enough  for  excavating;  but 
in  more  open  material  a  power  pump  is  usually  required. 

The  above  costs  are  the  actual  costs,  and  do  not  include  the 
contractor's  profits.  His  bid  on  the  work  was  as  follows : 

Piles  delivered 12  cts.  per  ft. 

Piles  driven $5  each 

Cofferdam $37  per  M. 

Wet  excavation $1.00  per  cu.  yd. 

Concrete $8.00  per  cu.  yd. 

In  order  to  ascertain  whether  or  not  these  prices  yielded  a 
fair  profit,  it  is  necessary  to  distribute  the  cost  of  the  plant 
transportation  and  rental  over  the  various  items.  We  have  al- 
lowed $120  for  plant  transportation  and  rental,  and  $70  for 
setting  up  and  taking  down  the  plant,  or  $190  in  all.  The 
working  time  of  the  plant  was  as  follows : 

Per  cent.  Prorated 
Days.         of  time,  plant  cost. 

Cofferdam 7  39  $74 

Excavation   2  1 1  21 

Foundation  piles 4  22  42 

Concrete    . « 5  28  53 

Totals    18  100  $190 

As  above  given,  the  labor  on  the  7,900  ft.  B.  M.  in  the  coffer- 
dam cost  $126,  or  $16  per  M. ;  but  this  additional  $74  of  pro- 
rated plant  costs,  adds  another  $9  per  M.,  bringing  the  total 
labor  and  plant  to  $25  per  M.,  to  which  must  be  added  the  $20 
per  M.  paid  for  the  timber  in  the  cofferdam,  making  a  grand 
total  of  $45  per  M.  This  shows  that  the  contractor's  bid  of 
$37  per  M.  was  much  too  low. 

The  labor  on  the  excavation  cost  57  cts.  per  cu.  yd.,  to 
which  must  be  added  the  prorated  plant  cost  of  $21  distributed 
over  the  58  cu.  yds.,  or  36  cts.  per  cu.  yd.,  making  a  total  of 
93  cts.  per  cu.  yd.  This  shows  that  the  bid  of  $i  per  cu,  yd. 
was  hardly  high  enough. 


BRIDGE  PIERS  AND  ABUTMENTS.  235 

The  labor  on  the  24  foundation  piles  cost  $80,  or  $3.33  each. 
The  prorated  plant  cost  is  $42,  or  $1.75  per  pile,  which,  added 
to  $3.33,  makes  a  total  of  $5.08.  This  shows  that  the  bid  of 
$5  per  pile  for  driving  was  too  low.  However  there  was  a 
profit  of  2  cts.  per  ft.,  or  80  cts.  per  pile,  on  the  cost  of  piles 
delivered. 

The  concrete  amounted  to  100  cu.  yds.  Hence  the  prorated 
plant  cost  of  $53  is  equivalent  to  53  cts.  per  cu.  yd.  Hence  the 
total  cost  of  the  concrete  was : 

Per  cu.  yd. 

Cement,  sand  and  stone .$3.20 

Foreman    (at  $5)    0.25 

Labor  (at  $2)  i  .00 

Engineman  (at  $3) 0.15 

Coal  (at  $3) 0.06 

Carpenters   (at  $3) 0.24 

Forms  (at  $23.50,  used  once)    0.80 

Wire,  nails,  etc 0.02 

Prorated  plant  cost 0.53 

Total    $6.25 

Since  the  contract  price  for  concrete  was  $8  per  cu.  yd., 
there  was  a  good  profit  in  this  item. 

BACKING  FOR  BRIDGE  PIERS  AND  ABUTMENTS. 

— Six  piers,  and  two  abutments  of  the  City  Island  bridge  were 
constructed  in  1906  at  New  York  city,  of  masonry  backed  with 
1-2-4  concrete  below  and  1-3-5  concrete  above  high  water.  The 
piers  and  abutments  were  all  sunk  to  rock  or  hard  material 
by  means  of  timber  cofferdams.  Table  XVI  gives  thelaborcost 
of  mixing  and  placing  the  concrete  backing  for  one  abutment 
and  three  piers,  after  the  materials  were  delivered  on  the 
scows.  The  concrete  was  mixed  by  a  rectangular  horizontal 
machine  mixer  and  deposited  by  2-cu.  yd.  bottom  dump  buck- 
ets handled  by  derrick  scows  and  stiff  leg  derricks.  The  high 
cost  of  concreting  on  Pier  2  was  due  to  the  fact  that  the  con- 
crete was  improperly  deposited  and  had  to  be  removed  and 
the  higher  cost  in  Abutment  I  was  probably  due  to  the  fact 
that  the  abutment  was  so  long  and  narrow  that  it  was  difficult 
to  handle  the  bucket. 


236 


CONCRETE    CONSTRUCTION. 


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BRIDGE  PIERS  AND   ABUTMENTS.  237 

PNEUMATIC  CAISSONS,  WILLIAMSBURG  BRIDGE. 

—Mr.  Francis  L.  Pruyn,  Assoc  M.  Am.  Soc.  C.  E.,  gives  the 
following  costs  of  concreting  the  pneumatic  caissons  for  the 
Brooklyn  tower  of  the  Williamsburg  bridge  at  New  York 
city.  The  work  comprised  the  mixing  and  placing  of  some 
13,637  cu.  yds.  of  concrete  in  two  caissons.  Table  XVII  shows 
the  itemized  costs  for  one  caisson  and  Table  XVIII  shows 
them  for  the  other  caisson.  The  methods  of  work  were  as 
follows : 

After  each  caisson  was  built  it  was  towed  to  its  proper  site, 
where  it  was  held  in  place  by  temporary  pile  dock  built  com- 
pletely around  it.  On  these  docks  the  concrete  was  placed ; 
a  2  cu.  yd.  cubical  mixer  of  the  usual  pattern  being  used  for 
mixing.  The  concrete  materials,  consisting  of  sand,  stone 
and  cement  was  handled  direct  from  barges  alongside,  into  the 
mixer.  The  concrete  was  placed  by  a  derrick  located  in  the 
center  ef  the  caisson,  which  was  a  bad  feature  as  the  caisson 
was  usually  out  of  level  and  considerable  difficulty  was  ex- 
perienced in  swinging  the  derrick.  On  the  South  caisson  ^4 
cu.  yd.  bottom  dump  buckets  were  used  in  placing  the  con- 
crete, on  the  North  caisson  the  size  of  these  was  increased 
to  i]/2  cu.  yd.  which  reduced  the  cost  of  placing  15  cts.  per  cu. 
yd.  There  were  placed  in  the  South  caisson  3,827  cu.  yds.  in 
32  days  of  actual  working  time — 120  cu.  yds.  per  day  of  10 
hrs.  The  gross  time  was  2  months.  On  the  North  caisson 
5,693  cu.  yds.  were  placed  in  46  days  worked — 124  cu.  yds. 
per  day.  The  gross  time  was  4  months. 

The  rates  of  labor  were  as  follows  per  lo-hour  day: 

Foreman $5-O° 

Assistant  foreman   2.50 

Hoisters    , 2.50 

Fireman    ." 1 .60 

Laborer    1-5° 

Proportions  concrete  were  i  :  2.5  : 6. 

The  low  price  of  sand  in  the  North  caisson  was  brought 
about  by  the  finding  of  good  building  sand  in  the  excavation 
for  the  anchorage,  which  work  was  done  by  the  same  con- 
tractor. 

When  the  caissons  had  been  sealed  the  iron  material  shafts 
were  removed.  This  left  holes  5  ft.  x  6  ft.  extending  from  the 


238  CONCRETE    CONSTRUCTION. 

roof  of  the  caisson  up  to  Mean  H.W.  which  were  filled  with 
concrete.  These  shaft  holes  were  80  ft.  deep  on  the  South 
caisson  and  100  ft.  deep  on  the  North  caisson.  They  were  par- 
tially filled  with  water  and  the  concrete  had  to  be  placed  with 
considerable  care.  Wooden  chutes  were  used  on  the  South 
caisson ;  they  rested  on  the  caisson  roof,  were  filled  with  con- 
crete and  then  raised  allowing  concrete  to  flow  out  at  the  bot- 
tom. The  shaft  holes  were  too  deep  on  the  North  caisson  for 
chutes  and  20  cu.  ft.  bottom  dump  buckets  were  used.  They 
had  to  be  lowered  to  bottom  of  shaft  each  trip  before  dump- 
ing, a  slow  operation,  which  greatly  added  to  the  cost.  Pro- 
portion for  concrete  1-2.5-6. 

The  proportion  for  concrete  in  working  chamber  was  the 
same  as  for  all  other  concrete.  The  specifications  called  for 
6  in.  of  mortar,  of  I  part  of  cement  to  2^2  parts  of  sand,  be- 
tween the  concrete  and  all  bearing  areas;  that  is,  under  the 
cutting  edge  and  directly  under  the  roof  of  the  working  cham- 
ber. The  concrete  was  mixed  in  the  cubical  mixer  and  dumped 
on  the  bottom  door  of  the  material  lock,  the  top  door  of  the 
lock  was  then  closed,  the  bottom  door  opened  and  the  con- 
crete fell  through  the  shaft  to  the  working  chamber.  It  was 
then  shoveled  by  the  sand  hogs  into  place.  A  6-in.  space  was 
left  below  all  bearing  surfaces  into  which  damp  mortar  was 
tightly  rammed.  Concreting  the  South  caisson  took  io}4 
working  days  of  24  hours,  the  gangs  working  night  and  day 
in  twelve  2-hour  shifts;  1,566  cu.  yds.  of  concrete  and  mortar 
were  placed,  or  at  the  rate  of  140  cu.  yds.  per  24  hours.  The 
gross  time  including  Sundays  was  14^2  days.  The  sand  hogs 
worked  in  shifts  of  2  hours  each  and  received  $3.50  for  the  two 
hours  work.  The  twelve  foremen  received  I  dollar  more ;  the 
average  gang  consisted  of  12  sand  hogs. 

On  the  North  caisson  the  organization  was  much  better, 
owing  to  the  experience  gained  on  the  first  caisson ;  and  in 
spite  of  the  fact  that  the  sand  hogs,  on  account  of  the  in- 
creased depth,  received  $4.00  for  il/2  hours'  work,  or  an  in- 
crease of  $22.00  per  man  per  24  hrs.  over  that  on  the  South 
caisson,  the  work  was  done  for  less  money.  There  were  placed 
1,566  cu.  yds.  of  concrete  in  7  working  days  of  24  hrs.,  or  at 
the  rate  of  224  cu.  yds.  per  day.  The  gross  time  was  nl/2 
days  including  Sundays.  The  average  number  of  men  in  the 


BRIDGE   PIERS  AND   ABUTMENTS. 


239 


sand  hog  gangs  was  18,  with  one  foreman,  who  received  $5 
for  il/2  hours  work. 

TABLE    XVII. — ITEMIZED    COST    OF    CONCRETING    SOUTH    CAISSON    FOR    BROOKLYN 

TOWER  OF  THE  WILLIAM SBURG  BRIDGE: 
COST  OF  CONCRETING  CAISSONS  ABOVE  ROOF. 

(South  Caisson   (3,827  cu.  yds.)- 


Materials. 
Cement    

Quantity. 
4,480  bbls. 
1,288  cu.  yds. 
.  3,421  cu.  yds. 

Rate. 
$1.57 
.60 
1.50 

Amount. 
$7,034.00 
773-00 
5,132.00 
36.00 

Sand    .           

Water  .-  

Total        

.  3,827  cu.  yds. 
.  3,827  cu.  yds. 

$3-39 
$0.90 

$12,975.00 

$3,432.00 
2,280.00 
742.00 

Labor. 
Mixing    and    placing              

Plant  charges         .                     .    .        . 

Plant  labor                 

Total    plant             .... 

3  827  cu  yds. 

$0.79 

$3,022.00 

Total  cost                        . 

.  3,827  cu.  yds. 
.  3,827  cu.  yds. 

$5-08 
•5i 

$19,429.00 
1,943.00 

General    expenses     10%         .       .  . 

Grand    total 

.  3,827  cu.  yds. 

riNG   SH'AFTS. 

Quantity. 
612^  bbls. 
193      cu.  yds. 
493       cu.  yds. 

$5-59        $21,372-00 

South  Caisson. 
Rate.          Amount. 
$1.57              $962.00 
.40                77.00 
i.io              542.00 

COST  OF  'CONCRE' 

Materials. 
Concrete    

Sand        

Stone           

Total                   

541       cu    yds 

$2.92 

$0.96 
i.  06 

$1,581.00 

$519-00 
576.00 

Labor. 
Handling    mixing  and  placing 

541       cu.  yds. 
541       cu.  yds. 

Plant    charges     etc 

Total 

541       cu.  yds. 
541       cu.  yds. 

$4.94 
•49 

$2,676.00 
267.00 

General  expenses    10% 

i 

Grand    total 

.541       cu.  yds. 

WORKING   CHAM 

South  Cais 
Quantity. 
.   1,666  bbls. 

$5-43 

BERS. 

son.     (1,435 
Rate. 
$1-57 
1-57 
.40 

I.IO 

$2,943.00 

cu.  yds.) 
Amount. 
$2,615.00 
720.00 
268.00 
1,299.00 

COST   OF  CONCRETE  IN 

Materials. 
Cement    for    concrete.  

Cement  for  mortar   

.      459  bbls. 
670  cu  yds. 

Sand   for  both  

Broken   stone 

1,181  cu    yds 

Total  materials                  .       .  .  • 

.    1,  4^  cu  yds 

$342 

$1.09 
4-93 
.19 

$4,902.00 

$1,575-00 
7,117-00 
275-00 

Labor. 
Top   labor    mixing  and  placing 

.    1  43s?  cu    vds 

Pneumatic   labor                       

.    1,4^  cu    vds 

Compressor  house  labor   

•   i,43S  cu.  yds. 

Total  labor    1,435  cu.  yds.        $6.21 


$8,967.00 


240 


CONCRETE    CONSTRUCTION. 


Plant. 

Coal  at  $2.40  per  ton. . . ., J,435  cu.  yds.  .10 

Concrete    plant    1,435  cu.  yds.  -79 

Pneumatic  plant   1,435  cu.  yds.  1.05 


140.00 
1,145.00 
1,522.00 


Total  plant    1,435  cu.  yds.  $1.94  $2,807.00 

Totals . 1,435  cu.  yds.  $n.57  $16,676.00 

General  expenses,   10% 1,435  cu.  yds.  1.16  1,667.00 

Grand  total    1,435  cu.  yds.  $12.73  $18,343.00 

TABLE    XVIII. — ITEMIZED    COST    OF    CONCRETING    NORTH    CAISSON    FOR  BROOKLYN 

TOWER   OF  THE    WILLIAMSBURG    BRIDGE  I 

COST    OF    CONCRETING    CAISSON    ABOVE    ROOF    (5,692  CU.    yds.) 

Materials.                                                 Quantity.  Rate.  Amount. 

Cement    6,707^  bbls.  $1.57  $10,531.00 

Sand   2,133      cu.  yds.  .40  845.00 

Broken   stone    4,938      cu.  yds.  i.io  5,432.00 

Water   51.00 

Total   5,692      cu.  yds.  $2.96  $16,859.00 

Labor. 

Mixing  and  placing   5,692      cu.  yds.  $0.73  $4,159.00 

Plant  charges   2,952.00 

Plant  labor 5 17.00 

Total 5,692      cu.  yds.  $0.61  $3,469.00 

Total   cost    5,692      cu.  yds.  $4.30  $24,487.00 

General  expenses,  10%    5,692      cu.  yds.  .43  2,448.00 

Grand  total    5,692      cu.  yds.  $4-73  $26,935.00 

COST  OF  CONCRETING   SHAFTS. 

Materials.                                                Quantity.  Rate.  Amount. 

Cement    614^  bbls.  $1.57  $965.00 

Sand    204      cu.  yds.  .40  82.00 

Stone   521       cu.  yds.  i.io  574-QO 

Total    576      cu.  yds.  $2.82  $1,621.00 

Labor. 

Mixing  and  placing 576      cu.  yds  1.70  982.00 

Plant  charges,  etc 576      cu.  yds.  1.36  795-OO 

Total    576      cu.  yds.  $5.88  $3,398.00 

General  expenses,  10%   576      cu.  yds.  .59  339.00 

Grand  total 576      cu.  yds.  $6.47  $3,737.oo 

COST    OF  CONCRETING    WORKING    CHAMBERS    ( 1,566  CU.    yds.). 

Materials.                                                Quantity.  Rate.  Amount. 

Cement  for  concrete  1,559      bbls.  $1.51  $2,446.00 

Cement  for  mortar    442      bbls.  1.51  $694.00 

Sand  for  both    630      cu.  yds.  .40  252.00 

Broken   stone    1,380      cu.  yds.  i.io  1,518.00 

Total    . . .' 1,566      cu.  yds.  $3.14  $4,910.00 

Labor  . 

Top  labor,  mixing  and  placing 1,566      cu.  yds.  $0.78  $1,198.00 

Pneumatic    labor    1,566      cu.  yds.  4.91  7,694.00 

Compressor  house  labor 1,566      cu.  yds.  .11  180.00 


Total  labor    1,566      cu.  yds.         $5.80 


$9,072.00 


BRIDGE  PIERS  AND  ABUTMENTS.  241 

Plant. 

Coal  at  $2.40  per  ton 1,566      cu.  yds.            .06  87.00 

Concrete  plant   1,566      cu.  yds.            .86  1,352.00 

Pneumatic   plant    1,566      cu.  yds.            .81  1,272.00 


Total  plant    1,566      cu.  yds.        $1-73          $2,711.00 

Totals    1,566      cu.  yds.      $10.67        $16,693.00 

General  expenses,  10% 1,566      cu.  yds.          1.06  1,669.00 


Grand  total  1,566      cu.  yds.      $11.73        $18,362.00 

COST  OF  FILLING  PIER  CYLINDERS.— The  following 
costs  were  obtained  in  mixing  and  placing  concrete  in  steel 
cylinder  piers.  The  sand  and  gravel  were  wheeled  100  ft.  to 
the  mixing  board  at  the  foot  of  the  cylinder,  mixed  and 
shoveled  into  wooden  skips,  hoisted  20  ft.  by  horsepower  and 
dumped  into  the  cylinder.  The  foreman  worked  on  the  mix- 
ing board  and  the  men  worked  with  great  energy.  The  costs 
were  as  follows : 

Item —  Per  day.  Per  cu.  yd. 

6  men  wheeling  materials  and  mixing  at  15 

cts.  per  hour  $9.00  $0.45 

2  men  dumping  skips  and  ramming  at  15  cts. 

per  hour  3.00  0.15 

I  team  and  driver  at  40  cts.  per  hour 4.00  0.20 

I  foreman  at  30  cts  per  hour 3.00  0.15 


Totals    $19.00  $0.95 

PIERS,  CALF  KILLER  RIVER  BRIDGE.— The  follow- 
ing methods  and  costs  of  building  two  new  piers  and  extending 
three  old  piers  with  concrete  are  given  by  Mr.  J.  Guy  Huff. 
The  work  was  done  by  the  railway  company's  masonry  gangs. 
Figure  94  shows  the  arrangement  of  the  several  piers  and  the 
character  of  the  work  on  each  and  Fig.  95  gives  the  detail  di- 
mensions of  the  three  main  piers. 

The  sand  and  aggregate,  consisting  of  blast  furnace  slag, 
were  unloaded  from  cars  to  platforms  on  a  level  with  the  top 
of  rail,  placed  about  100  ft.  south  from  the  south  end  of  the 
bridge.  A  cubical  1/6  cu.  yd.  mixer  was  used.  This  was  op- 
erated by  a  gasoline  engine,  and  was  located  on  a  platform 
about  50  ft.  south  of  the  south  end  pier.  A  tank  near  the 
mixer  to  supply  water  was  elevated  enough  to  get  the  desired 
head,  and  was  kept  filled  by  a  pump  run  by  another  gasoline 


242 


CONCRETE    CONSTRUCTION. 


Pier  No.  5 
Stone  Bcrse 
New  Concrete  Top 


entirely  New 
of  Concrete 


0 far  Ho.  3 
Stone     Base  • 
New  Concrete  Top 


iT^n^^W^ 

Pier  No.  2 

fntire/y  New 

of  Concrete 


Fig.   94.— Diagram  Arrangement  of  Piers,  Calf  Killer  River  Bridge. 

Base   of  ftait 


Fig. 


Plcm  and  Elevation  of  Piers  2, 3  and  4-. 
95.~Details  of  Pier  for  Calf  Killer  River  Bridge. 


BRIDGE   PIERS  AND   ABUTMENTS.  243 

engine  located  down  by  the  river  bank.     The  cement  house 
was  located  between  the  mixer  platform  and  slag  pile. 

Slag  and  sand  were  delivered  to  the  mixer  by  means  of 
wheelbarrows.  The  mixer  was  so  placed  that  it  would  dump 
onto  a  platform,  and  the  concrete  could  then  be  shoveled  into 
a  specially  designed  narrow-gage  car.  This  car  ran  on  one 
rail  of  the  main  track  and  an  extra  rail  outside.  A  turnout 
for  clearing  passing  trains  was  provided  at  both  ends  of  the 
bridge.  The  track  over  the  bridge  from  the  mixer  had  a  de- 
scending grade  of  about  I  per  cent.,  so  that  with  a  little  start 
the  concrete  car  would  roll  alone  down  to  the  required  points 
on  the  bridge.  Only  in  returning  the  empty  cars  to  the  mixer 
was  it  necessary  to  push  them  by  hand,  and  then  only  for  a 
distance  of  never  more  than  400  ft. 

Over  the  piers  on  the  bridge  in  the  center  of  the  concrete 
car  track  openings  were  sawed  to  let  the  concrete  pass  to  the 
forms  below.  To  get  the  concrete  into  the  forms,  there  were 
used  zigzag  chutes  with  arms  about  10  ft.  long,  which  sections 
were  removed  as  the  concrete  in  the  forms  was  increased. 
These  chutes  were  a  convenience  by  their  ends  alternating 
from  one  side  to  the  other  as  the  arms  were  removed  in  com- 
ing up. 

The  cost  of  the  concrete  work  was  as  follows: 
Unloading  Material. 

Rate     Total  days  Per  cu.  yd. 

per  day.     worked.     Total,     concrete. 

Foreman    $340  5          $17.00  $0.04 

ii  laborers 1.368/10     52  71.14  .15 

Total  for  unloading  material $0.19 

Building  Forms,  Bins,  Etc. 

Foreman    $340  18        $61.20  $0.14 

9  carpenters    2.25  166          373-5°  .81 

New  lumber,  23.7  M.  ft. 

at  $17.80 . .          421.86  .92 

Old  lumber,  6  M.  ft.  at 
$8.33 ..  49-98  ..ii 

Total  for  building  forms,  bins,  etc $1.98 


244  CONCRETE    CONSTRUCTION. 

Cofferdam  Excavation  (45  cu.  yds.) 

Foreman    $340  8          $27.20  $0.06 

9  laborers    1.156/10     74}^         86.12  .19 


Total  for  cofferdam  excavation  . . . . $0.25 

Cofferdam  Concrete  (37  cu.  yds.) 

Foreman    $340                8        $27.20  $0.06 

ii  laborers    1.363/10     79           107.68  .23 

Cofferdam  lumber,  2.25 

M.  ft.  at  $20.00 ."...,.          45.00  .09 

Total  for  cofferdam  concrete $0.38 

Concrete  Mixing  and  Placing. 

Foreman    $340              30        $102.00  $0.22 

9  laborers 1.15  6/10  282          325.99  .71 

Cement,    452     bbls.     at 

$i-55  ••• ,-:^.  701-50  !-52 

Slag,  437  cu.  yds.  at  $0.20    ...               ...            8740  .19 

Sand,  220  cu.  yds.  at 

$0.30    ..             66.00  .14 


Total  for  mixing  and  placing $2.78 

Taking  Down  Forms  and  Clearing  Up. 

Foreman .$340  13        $  44.20  $0.09 

ii  laborers  1.17  143  107.31  .36 

Total  for  taking  down  forms,  etc.. .  .$200.00            $045 
Engineering  and  supervision 43 


Grand  total,  460  cu.  yds.  concrete $6.46 

The  wages  given  are  the  average  wages.  The  men  worked 
a  lo-hour  day.  The  concrete  was  a  1-3-6  mixture.  The  cof- 
ferdam work  was  done  in  connection  with  the  construction 
of  the  fourth  pier,  this  pier  being  the  only  one  coming  in  the 
bed  of  the  river  to  be  built  entirely  new.  The  work  on  this 
was  started  in  water  about  6  ft.  deep.  The  37  cu.  yds.  of  con- 
crete is  included  in  the  total  of  460  cu.  yds.  in  the  above  tabu- 
lation. By  itself  the  cost  of  the  cofferdam  work,  not  includ- 
ing cost  of  cement,  sand  and  slag  was  as  follows : 


BRIDGE  PIERS  AND  ABUTMENTS. 


245 


Per  cu.  yd. 
Concrete. 
$1.21 
3.06 


Total. 

Lumber    $  45.00 

Labor,  excavating   113.32 

Labor,   concrete    134.88 


Total  37  cu.  yds.  concrete   $7.91 

METHOD  AND  COST  OF  CONSTRUCTING  21 
BRIDGE  PIERS.— The  following  account  of  the  methods  and 
cost  of  constructing  21  concrete  piers  for  a  railway  bridge  con- 


56 


*~r» 146- ^ 

Top    Plan. 


E/.I574.O8 


ffock 


Elevoi-Hon. 


End 

Elevation. 

Boxes  4'x4xj'9"lcf. 
made  ofJ"P/'ne  fo 
be  placed  where 
Anchor  Boli—ho/es 

A 

S1 

>^ 

<-:- 

Y 

!    f\ 

tl$----^5'0--^-4j%> 

iv  be  broken  <?uf 
when  Bofrs  are  sei~. 

Bo-tt-om    Plcxn- 

Fig.    96.— Details  of  Piers   for  K.    C.,   M.   &   O.   Ry.   Bridge. 

sisting  of  20  5O-ft.  plate  girder  spans  has  been  compiled  from 
records  kept  by  Mr.  W.  W.  Colpitts,  Assistant  Chief  Engineer, 
Kansas  City,  Mexico  &  Orient  Ry.  The  shape  and  dimensions 
of  the  piers  are  shown  by  Fig.  96  and  Fig.  97  shows  the  con- 
struction of  the  forms.  Sheet  pile  cofferdams  to  solid  rock 
were  used  for  constructing  the  foundations. 

The  1-3-5  concrete  was  mixed  in  a  Smith  mixer  having  a 
batch   capacity  of  9  cu.  ft.     The  mixer  was  located  on  the 


246 


CONCRETE    CONSTRUCTION. 


slope  of  the  embankment  approach,  with  the  main  track  at  its 
rear  and  facing  a  temporary  material  track.  This  temporary 
track  turned  out  from  the  main  track  about  500  ft.  beyond  the 
mixer  and  extended  diagonally  down  the  embankment  ap- 
proach on  a  3  per  cent,  grade  and  across  the  river  bottom 
alongside  the  pier  sites.  The  portion  of  the  track  in  the  river 
bottom  was  supported  on  bents  of  spliced  ties,  jetted  to  the 
rock,  and  wired  to  the  cofferdam  to  avoid  the  danger  of  loss  in 
case  of  high  water.  The  sand  and  crushed  rock  were  delivered 
by  cars  from  the  main  line  track,  immediately  above  the  mixer, 
and  the  cement  was  stored  in  a  shanty  at  one  side  of  the 


Enc 
Eelvu-li 


Nosed    Ends. 


Frame  6'be/ow  Top. 


Fig.   97.— Forms  for  Piers  for  K.    C.,   M.   &   O.   Ry.   Bridge. 

mixer.  The  concrete  materials  and  machinery  were,  in  this 
manner,  very  conveniently  located  for  rapid  work  and  well 
above  the  high  water  line.  The  concrete  was  transported  to 
the  pier  sites  in  improvised  dump  boxes,  set  on  push  cars. 
These  dump  boxes  were  hinged  longitudinally  and  discharged 
directly  into  the  cofferdams.  The  grade  of  the  temporary 
track  carried  the  push  cars  by  gravity  to  the  cofferdams 
and  they  were  returned  by  teams,  for  which  purpose  a  straw 
and  brush  road  had  been  built  paralleling  the  track.  As  the 
work  progressed  farther  into  the  stream,  more  cars  were 
added  properly  to  balance  the  work.  While  the  concrete  in 
the  base  was  still  fresh,  a  number  of  steel  reinforcing  bars,  8 


BRIDGE   PIERS  AND   ABUTMENTS.  247 

ft.  in  length,  were  set  in  place  along  each  end  to  insure  a  good 
bond  between  the  base  and  shaft. 

In  general,  the  work  of  putting  in  the  bases  was  organized 
so  that  about  the  same  time  was  required  in  filling  a  cofferdam 
with  concrete,  in  excavating  the  sand  from  the  next,  and  in 
driving  the  sheet  piling  for  the  third.  These  three  operations 
were  thus  carried  on  simultaneously  and,  although  interrup- 
tions in  one  part  of  the  work  or  the  other  occurred  fre- 
quently, the  gangs  were  interchangeable  and  no  appreciable 
loss  was  suffered,  except  in  time,  because  of  such  delays. 

In  piers  19  and  20,  where  the  rock  was  from  17  to  19  ft. 
below  the  surface,  some  difficulty  was  encountered  due  to  the 
presence  of  fissures  in  the  rock,  from  which  it  was  necessary 
to  remove  the  sand  to  fill  with  concrete.  In  such  cases,  the 
larger  leaks  were  stopped  as  much  as  possible  by  driving  sheet 
piles  against  the  outside  face  of  the  cofferdam  and  into  the 
fissures,  and  the  smaller  leaks  by  manure  in  canvas  bags 
rammed  into  the  openings. 

Upon  the  completion  of  all  the  bases,  the  forms  for 
several  shafts  were  set  in  position  and  the  work  of  filling  with 
concrete  proceeded  as  in  the  case  of  the  bases,  except  that  a 
derrick  erected  on  a  flat  car  and  stationed  at  the  pier  was 
utilized  to  raise  the. dump  boxes  in  depositing  the  concrete  in 
the  forms.  As  soon  as  the  concrete  in  one  shaft  had  set  suffi- 
ciently to  permit  of  it,  the  forms  were  removed  and  placed  on 
the  pier  ahead.  Four  sets  of  forms  were  used  for  the  shafts. 

The  following  are  the  average  prices  paid  for  materials  and 
labor: 

Materials. — Lumber  for  forms,  etc.,  $16.50  per  M.  ft.,  B.  M. ; 
cement,  Kansas  Portland,  $1.50  per  bbl. ;  broken  limestone, 
45c  per  cu.  yd.;  sand,  Arkansas  River,  I5c  per  ton. 

Labor. — General  foreman,  $110  per  month;  assistant  fore- 
man, $75  per  month ;  timekeeper,  $60  per  month ;  riveters,  350 
per  hour;  blacksmith,  3oc  per  hour;  blacksmith  assistant,  2oc 
per  hour;  carpenters,  22>^c  and  25c  per  hour;  enginemen,  25c 
per  hour;  firemen,  2oc  per  hour;  night  watchman,  2oc  per 
hour;  laborers,  17^2  c  and  200  per  hour;  team  (including 
driver),  4oc  per  hour.  The  prices  quoted  for  lumber,  cement, 
limestone  and  sand  are  prices  f.  o.  b.,  Louisiana,  lola,  Kan., 
El  Dorado,  Kan.,  and  Wichita,  Kan. 


248  CONCRETE    CONSTRUCTION. 

The  total  and  unit  cost  of  constructing  the  concrete  piers 
and  abutments  and  of  erecting  the  steel  superstructure  are 
given  in  the  following  tabulation.  Altogether  there  was  about 
2,300  cu.  yds.  of  concrete  in  the  substructure,  most  of  which, 
as  stated  above,  was  a  1-3-5  mixture. 

Machinery  and  Supplies. 

Concrete  mixer,  20%  of  cost .$    152.10 

Supplies,  freight,  hauling,  setting  up 505.04 


Total    $  657.14 

Centrifugal  sand  pump,  20%  of  cost $  27.00 

Supplies,  freight,  hauling,  setting  up 277-5° 

Rent  of  traction  engine  to  operate 83.25 


Total    .......$    387.75 

Water  pump  and  pipe,  20%  of  cost $      29.00 

Supplies,  freight,  hauling,  setting  up 177.32 


Total $    206.32 

Pile  driver  engine,  20%  of  cost $    100.00 

Supplies,  freight,  hauling,  setting  up 243.65 


Total    i $    343-65 


Grand  total $1,594.86 

Cofferdams. 

Materials,  lumber  and  nails $1,285.26 

Freight  and  train  haul 306.33 

Labor  making  piles . 696.82 

Labor  driving  piles i  ,384.05 


Total $3,672.46 

The  sheet  piling  took  63,500  ft.  B.  M.  of  lumber ;   the  cost 
per  i ,000  ft.  B.  M.  for  the  sheet  piling  was  then: 

Materials,  lumber  and  nails   $     20.08 

Freight  and  haulage 4.82 

Labor   making   piles 10.97 

Labor  driving  piles  21.80 


Total    $      57.67 


BRIDGE   PIERS  AND   ABUTMENTS. 


249 


Forms,  Platforms  and  Runways. 

Lumber,  hardware,  etc. . $  224.59 

Freight  and  train  haul .  .  40.20 

Labor  making,  removing  and  placing 556.51 


Total    $    821.30 

Concrete  Materials. 

Cement,  freight,  unloading  and  storing $4,617.48 

Sand,  freight,  unloading,  etc 1,336.05 

Broken  stone,  freight,  unloading,  etc 2,026.92 


Total .$7,980.45 

This  gives  us  for  2,300  cu.  yds.  of  concrete  a  cost  of  $3.47 
per  cu.  yd.  for  materials,  including  freight,  storage,  and  un- 
loading charges  of  all  kinds.  A  line  on  the  proportion  of  the 
cost  contributed  by  these  latter  items  may  be  got  by  taking 
the  prices  of  the  materials  f.  o.  b.  at  the  places  of  production 
and  assuming  the  proportions  for  a  1-3-5  concrete.  According 
to  tables  in  Chapter  II,  a  1-3-5  broken  stone  concrete  requires 
per  cubic  yard  1.13  bbls.  cement,  0.48  cu'.  yd.  sand  and  0.80  cu. 
yd.  broken  stone.  We  have  then  : 

1.13  bbls.  cement,  at  $1.50 $1.69 

0.48  cu.  yd.  sand,   at   2oc 10 

0.80  cu.  yd.  stone,    at   45c 36 


Total  $2.15 

This  leaves  a  charge  of  $1.32  per  cubic  yard  of  concrete  for 
freight  and  handling  materials.  The  cost  of  mixing  concrete 
and  placing  it  in  the  forms  was  $3,490.87,  or  $1.52  per  cu.  yd. 
We  have  then : 

Cost  of  concrete  materials  per  cu.  yd $3-47 

Cost  of  mixing  and  placing  concrete 1.52 

Total $4.99 

The  miscellaneous  expenses  of  the  work  comprised : 

Watchman,  tools,  telephone,  etc $    722.48 

Shanties,  furnishings,  supplies,  etc 829.04 


Total    $i,55l-52 


250  CONCRETE    CONSTRUCTION. 

To  this  has  to  be  added  $1,134.28,  the  cost  of  excavating  the 
cofferdams.  The  total  and  unit  costs  of  the  different  items  of 
the  concrete  substructure  work  can  now  be  summarized  as 
follows : 

Item.  Total.  Per  cu.  yd. 

Machinery  and  supplies $  1,594.86  $  .69 

Cofferdams  3,672.49  1.60 

Forms,  etc 821.30  .36 

Concrete  materials  . . .  . 7,980.45  3.47 

Mixing  and  placing  concrete 3,490.87  "1.53 

Excavating  cofferdams 1,134.28  .49 

Miscellaneous  1,551.52  .67 


Totals   $20,245.74  $8.81 

COST  OF  PERMANENT  WAY  STRUCTURES  KAN- 
SAS CITY  OUTER  BELT  &  ELECTRIC  RY.— The  follow- 
ing cost  of  concrete  work  including  retaining  walls,  abutments 
and  box  culverts,  for  the  permanent  way  of  the  Kansas  City 
Outer  Belt  &  Electric  Ry.,  is  given  by  Mr.  W,  W.  Colpitts. 
These  figures  are  of 'particular  interest,  for  the  variation  in 
prices  of  materials  during  the  two-year  period  while  work  was 
in  progress  and  as  giving  the  average  cost  of  the  work  on  the 
whole  line  as  well  as  for  individual  structures.  The  culverts 
were  all  box  culverts  with  wing  walls  and  the  abutments  were 
for  girder  bridges.  Walls  and  abutments  were  of  L  section 
with  triangular  or  trapezoidal  counterforts  at  the  back  be- 
tween base  slab  and  coping.  The  form  work  was  thus  rather 
complex. 

All  work  was  reinforced  concrete,  and  was  done  by  contract 
under  the  following  conditions :  The  work  of  preparing 
foundations,  including  excavation,  pile  driving,  diversions  of 
streams,  etc.,  was  done  by  the  railroad  company,  which  also 
bore  one-half  the  cost  of  keeping  foundations  dry  while  forms 
were  being  built  and  concrete  placed.  The  railroad  company 
also  furnished  the  reinforcing  bars  at  the  'site  of  each  opening. 
The  concrete  work  was  let  at  $9  per  cu.  yd.,  which  figure  cov- 
ered all  the  labor  and  materials  necessary  to  complete  the 
work,  other  than  the  exceptions  mentioned.  The  concrete 
proportions  were  1-3-5.  The  cement  used  was  Tola  Portland 


BRIDGE   PIERS   AND   ABUTMENTS.  2$l 

and  Atlas  Portland.  The  sand  was  obtained  from  the  bed  of 
the  Kansss  River  in  Kansas  City.  The  rock  used  was  crushed 
limestone,  passing  a  2-in.  ring  and  freed  from  dust  by  screen- 
ing. Corrugated  reinforcing  bars,  having  an  elastic  limit  of 
from  50,000  to  60,000,  Ibs.  per  sq.  in.,  manufactured  by  the  Ex- 
panded Metal  &  Corrugated  Bar  Co.  of  St.  Louis,  Mo.,  were 
used  exclusively.  The  concrete  in  the  smaller  structures  was 
mixed  by  hand,  in  the  larger  by  a  No.  i  Smith  mixer.  In  the 
first  structures  built  2-in.  form  lumber  was  used,  with  2  by 
6-in.  studs  placed  3  ft.  on  centers.  This  was  abandoned  later 
for  i-in.  lumber  with  2  by  6-in.  studs,  12  ins.  on  centers,  and 
was  found  to  be  more  satisfactory  in  producing  a  better  face. 
The  structures  were  built  in  the  period  from  April,  1905,  to 
May,  1907. 

The  cost  of  materials   and  the  wages  paid  labor  were  as 
follows : 

Cement — 

Per  barrel  at  structure,  April,  1905 $1.25 

Per  barrel  at  structure,  April,  1907 1.92 

Average  cost  per  barrel  at  mill 1.42 

Freight  per  barrel   0.21 

Hauling  il/2  miles  and  storage 0.12 

Average  cost  at  structure 1.75 

Average  cost  per  cu.  yd.  concrete  (i.i  bbls.) 1.93 

Sand — 

Per  cu.  yd.  at  structure,  April,  1905 $0.625 

Per  cu.  yd.  at  structure,  April,  1907 0.75 

Average  cost  per  cu.  yd.,  river  bank °-3° 

Freight  per  cu.  yd 0.22 

Hauling  1 1/2  miles 0.20 

Average  cost  at  structure 0.72 

Average  cost  per  cu.  yd.  concrete  (^2  cu.  yd.) O-3^ 

Stone — 

Per  cu.  yd.  at  structure,  April,  1905 $  i.io 

Per  cu.  yd.  at  structure,  April,  1907 1-75 

Average  cost  per  cu.  yd.  at  crusher 0.65 

Hauling  4  miles   : 0.84 

Average  cost  at  structure 1-49 

Average  cost  per  cu.  yd.  concrete  (0.9  cu.  yd.) 1.34 


252 


CONCRETE    CONSTRUCTION. 


Lumber — 

Per  M.  ft.  at  structure,  April,  1905 $15.00 

Per  M.  ft.  at  structure,  April,  1907 22.50 

Average  cost  per  M.  at  structure 19.00 

Average  cost  per  cu.  yd.  concrete. .  . . 0.49 

Labor—  Max.  Min. 

Common  labor,  cts.  per  hour 20  17 

Carpenters,  cts.  per  hour 40  30 

With  these  prices  and  wages  the  average  cost  of  concrete 
work  for  the  whole  line  was : 

Item.  Per  cu.  yd. 

Form  building  and  removing. $1.98 

Mixing  and  placing  concrete 0.74 

Placing  reinforcement o.io 

Wire,  nails,  water,  etc 0.20 

i.i  bbls.  cement  at  $1.75 1.93 

l/2  cu.  yd.  sand  at  $0.72 0.36 

0.9  cu.  yd.  stone  at  $1.49 1.34 

Lumber  for  forms O-49 

Total    $7.14 

The  following  are  the  costs  of  specific  structures  built  at 
different  times : 

Example  I. — Indian  Creek  Culvert.  14x15  ft.,  250  long, 
completed  November,  1905 : 

Per  cu.  yd. 

Cement $1-37 

Sand 34 

Stone    i.io 

Labor    2.48 

Lumber   76 

Miscellaneous 18 

Total    $6.23 

nxample  II. — Third  Street  Abutments  and  Retaining  Wall. 
Completed  November,  1906: 


BRIDGE   PIERS  AND   ABUTMENTS.  253 

Per  cu.  yd. 

Cement    $1.78 

Sand    35 

Stone 1.35 

Lumber    74 

Labor    2.75 

Miscellaneous 16 

Total    $7.13 

Example  III. — Abutments,  Overhead  Crossing  with  Union 
Pacific  and  Rock  Island.    Completed  May,  1907 : 

Per  cu.  yd. 

Cement    §i  .92 

Sand 32 

Stone    i .74 

Lumber 98 

Labor    2.96 

Miscellaneous 16 

Total .$8.08 

COST  OF  PLATE  GIRDER  BRIDGE  ABUTMENTS.— 

The  following  record  of  the  construction  of  20  abutments  for 
10  four-track  plate  girder  bridges  over  streets  in  Chicago,  111., 
are  given  by  Mr.  W.  A.  Rogers.  The  work  was  done  between 
May  i  and  Oct.  i,  1898,  in  which  time  8,400  cu.  yds.  of  concrete 
were  placed,  all  the  work  being  done  by  company  labor.  The 
forms  were  made  of  2-in.  plank  and  6x6-in.  posts  bolted  to- 
gether at  the  top  and  bottom  with  ^-in.  rods.  The  lumber 
was  used  over  and  over  again.  When  the  dressed  plank  be- 
came too  poor  for  the  face  it  was  used  for  the  back.  The  con- 
crete was  i  Portland  cement,  3  gravel  and  4  to  4^2  limestone 
(crusher  run  up  to  3-111.  size).  A  mortar  face  il/2  ins.  thick 
was  built  up  with  the  rest  of  the  concrete.  The  concrete  was 
made  quite  wet,  and  each  man  ramming  averaged  18  cu.  yds.  a 
day  rammed.  The  concrete  was  mixed  by  a  machine  of  the 
Ransome  type,  operated  by  a  I2-HP.  portable  gasoline  engine. 
The  load  was  very  light  for  the  engine,  and  8  HP.  would  have 
been  sufficient.  The  engine  made  235  revolutions  per  minute, 
and  the  pulley  wheels  were  proportioned  so  that  the  mixer 


254  CONCRETE    CONSTRUCTION. 

made  12  revs,  per  minute.  One  gallon  of  gasoline  was  used 
per  hour,  and  the  mixing  was  carried  on  day  and  night  so  as 
not  to  give  the  concrete  time  to  set.  The  time  required  for 
each  batch  was  2  to  3  mins.,  and  about  J^  cu.  yd.  of  concrete 
was  delivered  per  batch.  The  average  output  was  70  cu.  yds. 
per  lo-hr.  shift,  with  a  crew  of  28  men  ;  but  as  high  as  96  cu. 
yds.  were  mixed  in  10  hrs.  The  concrete  was  far  superior  to 
hand  mixed  concrete.  The  water  for  the  concrete  was  meas- 
ured in  an  upright  tank  and  discharged  by  a  pipe  into  the 
mixer.  The  sand  and  stone  were  delivered  to  the  mixer  in 
wheelbarrows,  and  the  concrete  was  taken  away  in  wheelbar- 
rows. No  derricks  were  used  at  all.  Each  wheelbarrow  of 
concrete  was  raised  by  a  rope  passing  over  a  pulley  at  the 
top  of  a  gallows  frame,  one  horse  and  a  driver  serving  for 
this  raising.  A  small  gasoline  hoisting  engine  would  have 
been  more  satisfactory  than  the  horse  which  was  worked  to  its 
full  capacity.  After  the  barrows  were  raised  (12  ft.),  they 
were  wheeled  to  the  abutment  forms  and  dumped.  The  empty 
wheelbarrows  were  lowered  by  hand,  by  means  of  a  rope 
passing  over  a  sheave  and  provided  with  a  counterweight  to 
check  the  descent  of  the  barrow.  The  cost  of  the  concrete 
(built  by  company  labor)  was  as  follows : 

Per  cu.  yd. 

Cement,  gravel  and  stone  delivered $3-28 

Material  in  forms  (used  many  times) n 

Carpenters  building  and  taking  down  forms 34 

Labor 1.18 

Total  per  cu.  yd $4-9* 

The  labor  cost  includes  moving  plant  from  one  bridge  to  the 
next,  building  runways,  gasoline  for  engine,  oil  for  lights  at 
night  and  unloading  materials,  as  well  as  mixing,  transporting 
and  placing  concrete.  Wages  were  $1.75  per  lo-hour  day  for 
laborers  and  $2.50  for  carpenters. 

COST  OF  ABUTMENTS  AND  PIERS,  LONESOME 
VALLEY  VIADUCT.— Mr.  Gustave  R.  Tuska  gives  the  fol- 
lowing on  the  concrete  substructure  of  the  Lonesome  Valley 
Viaduct,  near  Knoxville,  Tenn.  There  were  two  U-shaped 
abutments  and  36  concrete  piers  made  of  a  light  limestone 
that  deteriorates  rapidly  when  used  for  masonry.  Derricks 


BRIDGE   PIERS  AND   ABUTMENTS.  255 

were  rtot  needed  as  would  have  been  the  case  with  masonry 
piers,  and  colored  labor  at  $i  for  n  hrs.  could  be  used.  The 
piers  were  made  4  ft.  square  on  top,  from  5  to  16  ft.  high,  and 
with  a  batter  of  i  in.  to  the  foot.  The  abutments  average 
26  ft.  high,  26  ft.  long  on  the  face,  with  wing  walls  27  ft.  long ; 
the  wall  at  the  bridge  seat  is  5  ft.  thick,  and  the  wing  walls 
are  3^/2  ft.  wide  on  top.  Batters  are  I  in.  to  the  foot. 

The  forms  were  ma'de  of  2-in.  tongued  and  grooved  plank, 
braced  by  posts  of  2  x  lo-in.  plank  placed  3  ft.  c.  to  c.  for  the 
abutments,  and  at  each  corner  for  the  piers.  At  the  corners 
one  side  was  dapped  into  the  other,  so  as  to  prevent  leakage 
of  cement.  The  posts  were  braced  by  batter  posts  from  the 
earth.  For  the  piers  a  square  frame  was  dropped  over  the 
forms  and  spiked  to  the  posts.  The  abutment  forms  were 
built  up  as  the  concreting  progressed.  The  north  abutment 
forms  were  made  in  sections  6  ft.  high,  held  by  J^-in.  bolts 
buried  in  the  concrete.  The  lower  sections  were  removed 
and  used  again  on  the  upper  part  of  the  work,  thus  saving 
plank.  The  inside  of  forms  was  painted  with  a  thin  coat  of 
crude  black  oil.  The  same  form  was  used  for  several  piers. 

The  concrete  was  1-2-5,  the  barrel  being  the  unit  of  measure, 
making  about  £4  cu-  yd.  of  concrete  per  batch.  The  mortar 
was  mixed  with  hoes,  but  shovels  were  used  to  mix  in  the 
stone.  By  passing  the  blade  of  a  shovel  between  the  form 
and  the  concrete,  the  stone  was  forced  back  and  a  smooth 
mortar  face  was  secured.  Rammers  weighing  30  to  40  Ibs. 
were  used  for  tamping.  Two  days  after  the  completion  t>f  a 
pier  the  forms  were  removed.  The  concrete  was  protected 
from  the  sun  by  twigs,  and  was  watered  twice  a  day  for  a 
week.  It  was  found  by  actual  measurement  that  i  cu.  yd.  t>f 
concrete  (1-2-5),  the  ingredients  being  measured  in  barrels, 
consisted  of  i*4  bbls.  of  Atlas  cement,  10  cu.  ft.  of  sand,  and 
26^2  cu.  ft.  of  stone.  The  total  amount  of  concrete  was  926 
cu.  yds.  of  which  two-thirds  was  in  the  two  abutments.  The 
work  was  done  (in  1894)  by  contract,  for  $7  per  cu.  yd., 
cement  costing  $2.80  per  bbl.,  sand  30  cts.  per  cu.  yd.,  and 
wages  $i  a  day.  A  slight  profit  was  made  at  this  price.  A 
gang  of  15  men  and  a  foreman  would  mix  and  lay  about  40 
cu.  yds.  in  ii  hrs.  when  not  delayed  by  lack  of  materials.  The 
cost  of  making  the  concrete,  with  wages  at  $i  a  day,  was : 


256  CONCRETE    CONSTRUCTION. 

Cts.  per 
cu.  yd. 

1  man  filling  sand  barrels  and  handling  water 2.7 

2  men  filling  rock  barrels 5.4 

4  men  mixing  sand  and  cement 10.6 

4  men  mixing  stone  and  mortar 10.6 

2  men  wheeling  concrete 5.3 

i  man  spreading  concrete    2.7 

I  man  tamping 2.7 

I  foreman    5.0 

Total  labor   45.0 

COST  OF  HAND  MIXING  AND  WHEELBARROW 
WORK  FOR  FOUR  BRIDGE  PIERS.— The  following  fig- 
ures of  the  cost  of  hand-mixed  concrete  for  bridge  piers  and 
abutments  are  given  by  Mr.  Fred  R.  Charles  of  Richmond, 
Ind.  The  figures  cover  three  jobs.  All  concrete  was  mixed 
by  hand  and  with  one  exception  noted  below  was  moved  to 
place  in  wheelbarrows.  The  concrete  was  a  1-2^-5^  mix- 
ture. In  this  connection  it  is  well  to  note  that  in  one  or  two 
of  the  jobs  where  the  proportion  of  the  aggregate  seems  too 
small  for  the  yardage  of  concrete  the  difference  is  accounted 
for  by  the  fact  that  large  stones  were  placed  in  the  founda- 
tions, these  stone  being  on  the  ground  and  costing  nothing 
but  the  labor  to  throw  them  in. 

Job  I. — The  first  job  consisted  of  the  construction  of  one 
abutment  and  six  piers  for  a  bridge  over  the  Miami  River  at 
Fernald,  O.  The  stone  was  procured  on  the  site  and  crushed 
by  a  portable  crusher  run  by  a  traction  engine.  The  rough 
stone  cost  10  cts.  a  cubic  yard,  and  this,  with  the  cost  of 
handling,  fuel  and  hire  of  engine  and  crusher,  made  the  cost  of 
crushed  stone  about  $i  per  cu.  yd.  Sand  was  obtained  close  to 
the  work,  but  the  cement  had  to  be  teamed  10  miles.  Labor 
was  paid  $1.75  per  day.  The  cost  of  materials  and  labor  per 
cubic  yard  of  concrete  in  place  was  as  follows: 


UNIVERSITY 


BRIDGE   PIERS  AND   ABUTMENTS. 


257 


Item.  Per  cu.  yd. 

1.16  bbls.  cement  at  $2.10 $1.58 

Sand 0.35 

Stone ^. 0.75 

Lumber   " 0.64 

Tools,   hardware,    etc -. 0.20 

Labor  (including  15  cts.  per  cu.  yd.  for  pumping) 2.78 

Total  materials  and  labor $6.30 

Job  II. — The  second  job  was  the  construction  of  two  abut- 
ments containing  434  cu.  yds.  of  concrete  for  a  viaduct  at 
Ernst  Street,  Cincinnati,  O.  The  abutments  were  constructed 
at  the  street  and  the  excavation  was  clay  and  shale.  Labor 
received  $1.75  per  day.  The  cost  of  materials  and  labor  per 
cubic  yard  of  concrete  in  place  was  as  follows : 

Materials —  Per  cu.  yd. 

376  bbls.  cement  at  $1.70 $1.48 

224  cu.  yds.  sand  at  $1.20 0.64 

255  cu-  yds.  stone  at  $1.55 i.oo 

Lumber 0.40 

Tools,  hardware,  etc 0.06 

Total  materials   .......... $3.58 

Labor — 

Clearing   and    excavating $1.12 

Mixing  and  placing  concrete 1.13 

Building  forms,  etc 0.25 

I;  Total  labor   -. $2.50 

Total  labor  and  materials $6.08 

Job  III. — This  job  consisted  in  placing  570  cu.  yds.  of  con- 
crete in  the  pedestals  for  a  viaduct  at  Quebec  Avenue,  Cincin- 
nati, O.  The  pedestals  were  5  ft.  square  on  top  and  from  8  to 
20  ft.  high.  The  location  of  the  work  was  very  inconvenient 
for  the  delivery  of  materials,  all  materials  having  to  be  teamed 
or  wheeled.  Labor  was  paid  $1.75  per  day.  The  cost  of  labor 
and  materials  per  cubic  yard  of  concrete  in  place  was  as 
follows : 


258  CONCRETE    CONSTRUCTION. 

Item.  Per  cu.  yd 

500  bbls.  cement  at  $1.60. $1.40 

239  cu.  yds.  sand  at  $1.25. 0.53 

560  cu.  yds.  stone  at  $1.88 1.84 

Lumber    . . . 0.38 

Tools,  hardware,  etc .  . . .  . 0.05 

Labor 2.96 


Total  labor  and  materials $7.16 

Job  IV. — This  job  consisted  in  placing  2,111  cu.  yds.  of 
concrete  in  a  railway  viaduct  at  Cincinnati,  O.  For  one  pier 
56  ft.  high  the  concrete  was  raised  to  place  by  a  derrick ;  for 
the  remainder  of  the  work  it  was  wheeled  or  teamed  to  place. 
Labor  was  paid  $1.75  per  day.  The  cost  of  labor  and  materials 
per  cubic  yard  of  concrete  in  place  was  as  follows : 

Item.  Per  cu.  yd. 

1,908  bbls.  cement  at  $1.60 $1-44 

1,105  cu-  yds.  sand   at  $1.95 , 0.50 

1,468  cu.  yds.  stone  at  $1.48 , 1.03 

Lumber 0.54 

Tools,  hardware,  etc. . .  .  „ 0.25 

Water 0.03 

Labor , 3.44 


Total  labor  and  materials .$7.23 


CHAPTER    XIII. 

METHODS  AND  COST  OF  CONSTRUCTING  RETAIN- 
ING WALLS. 

Concrete  retaining  walls  may  for  construction  purposes  be 
divided  into  two  classes :  Plain  concrete  Trails  of  gravity  sec- 
tion and  reinforced  concrete  walls  consisting  of  a  thin  slab 
taking  the  thrust  of  the  earth  as  a  cantilever  anchored  to  a 
base  slab  or  as  a  flat  beam  between  counterforts.  The  rein- 
forced wall  requires  much  less  concrete  for  a  given  height 
than  does  the  plain,  gravity  wall,  but  the  concrete  is  more  ex- 


EN6.NEW6.  ;     Jl  ;     .  j,, 

I     jtt/t  |-         tw  nv      | 

Elevation.  K7#-»K tO'0* -X 

Section. 

Fig.    98. — Comparison  of  Plain   and  Reinforced   Sections   for  Retaining  Walls 

(C.    E.    Graff). 

pensive  ojving  to  the  reinforcement  and  to  the  more  complex 
form  of  construction,  and,  in  some  measure,  to  the  greater  cost 
of  placing  the  mixture  in  narrow  forms  and  around  reinforce- 
ment. It  is  common,  too,  to  require  a  richer  concrete  for  the 
reinforced  than  for  the  plain  wall. 

COMPARATIVE  ECONOMY  OF  PLAIN  AND  REIN- 
FORCED CONCRETE  WALLS.— Prior  to  the  construction 
of  some  2,000  ft.  of  retaining  wall  ranging  in  height  from  2  ft. 

259 


2(5o 


CONCRETE    CONSTRUCTION. 


to  38  ft.,  at  Seattle,  Wash.,  calculation  was  made  by  the  en- 
gineers of  the  Great  Northern  Ry.  to  determine  the  compara- 
tive economy  of  plain  concrete  and  reinforced  concrete  sec- 
tions. The  sections  assumed  were  those  shown  by  Fig.  98,  and 
comparisons  were  made  at  heights  of  10,  20,  30  and  40  ft.,  with 
the  following  results : 

Height  in  Plain.  Reinforced.         Per  cent, 

feet.  Cu.  yds.  per  ft.     Cu.  yds.  per  ft.         Saving. 

10    1.63  1.29  20.4 

20    4.08  2.59  36.4 

30    8.40  4.73  43.3 

40    1470  8.07  45.0 

The  saving  in  concrete  increased  as  the  height  of  the  wall 
increased ;  for  a  4O-ft.  wall  reinforced  concrete  at  nearly 
double  the  cost  per  cubic  yard  in  place  would  be  as  cheap  as 
plain  concrete. 

Top  of Mo*.'Surchorqt  Tof  of  Max  Surcharge 


Fig.    99. — Comparison   of   Plain   and  Reinforced    Sections   for  Retaining  Wall 

(F.   F.   Sinks). 


Taking  substantially  the  section  of'  reinforced  wall  being 
used  on  the  Chicago  track  elevation  work  of  the  Chicago,  Bur- 
lington &  Quincy  R.  R.,  and  comparing  it  with  a  plain  wall  as 
shown  by  Fig.  99,  Mr.  F.  F.  Sinks  obtained  the  following 
results : 

Plain  Wall,  Cost  per  Lineal  Foot — 

4.8  cu.  yds.  concrete  at  $4 $19.20 

115  ft.  B.  M.  of  forms  at  $31 3.56 


Total  4.8  cu.  yds.  at  $474 $2276 


RETAINING   WALLS. 


26l 


Reinforced  Wall,  Cost  per  Lineal  Fdot — 

3.46  cu.  yds.  concrete  at  $4.10 $14.18 

115  ft.  B.  M.  of  forms  at  $31 3.56 

109  Ibs.  reinforcing  steel  at  3 j4  cts 3-54 

1.34  cu.  yds.  extra  fill  at  20  cts 0.27 

0.32  cu.  yd.  extra  excavation  at  20  cts 0.06 

Total,  3.46  cu.  yds.  concrete  at  $6.25 $21.61 

The  saving  in  this  case  was  $1.15  per  lineal  foot  of  wall  with 
the  unit  cost  of  reinforced  concrete  in  place  24  per  cent, 
greater  than  the  unit  cost  of  plain  concrete.  It  will  be  noted 
that  there  is  some  28  per  cent,  less  concrete  per  lineal  foot  of 
wall  in  the  reinforced  section  and  also  that  this  section  is  so 
designed  that  the  form  work  is  about  as  simple  for  one  section 


EUtt 


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1                                  H 

L 
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t                i 

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-    10'  0'  -      —  J--^--M 

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1«  —               c'n"                                               TV?"    _ 

Fig.   100. — Forms  for  Retaining  Wall  Work,  N.   Y.   C.  &  H.  R.  R.   R. 

as  for  the  "other.  Another  point  to  be  noticed  is  that  there  is 
no  saving  in  excavation  by  using  a  reinforced  section  instead 
of  a  gravity  section,  in  fact  the  excavation  runs  slightly  more 
for  the  reinforced  section. 

FORM  CONSTRUCTION.— Retaining  wall  work  often 
affords  an  opportunity  for  constructing  the  forms  in  panels 
and  this  opportunity  should  be  taken  advantage  of  when  pos- 
sible. Several  of  the  walls  described  later  give  examples  of 
form  work  that  may  be  studied  with  profit  in  this  respect. 

Figure  100  shows  a  panel  form  construction  employed  on 
the  New  York  Central  &  Hudson  River  R.  R.  The  3x8-in. 
studs  are  erected,  care  being  taken  to  get  them  in  proper  line 
and  to  true  batter  and  also  to  brace  them  rigidly  by  diagonal 
props.  Generally  the  studding  is  erected  for  a  section  of  wall 


CONCRETE    CONSTRUCTION. 

50  ft.  long  at  one  time.  The  lagging-,  made  in  panels  2*4  ft. 
wide  and  10  ft.  long,  by  nailing  2-in.  plank  to  2  x  4-111.  cleats, 
is  attached  to  the  studding  a  panel  at  a  time  and  beginning 
at  the  bottom,  by  means  of  the  straps,  wedges  and  blocks 
shown.  Five  bottom  panels  making  a  form  2^  ft.  high  and 
50  ft.  long  are  placed  first.  When  the  concrete  has  been 
brought  up  nearly  to  the  top  of  these  panels,  a  second  row 
of  panels  is  placed  on  top  of  the  first.  When  it  is  judged  that 
the  concrete  is  hard  enough  the  lowermost  panels  are  loosened 
and  made  free  by  removing  the  wedges,  blocks  and  straps 
and  the  panels  are  drawn  out  endwise  from  behind  the  stud- 
ding and  used  over  again  for  one  of  the  upper  courses.  The 
small  size  of  the  panels  makes  it  practicable  to  lay  bare  the 
concrete  while  it  is  yet  soft  enough  to  work  with  a  float  or  to 
finish  by  scrubbing  as  described  in  Chapter  VIII.  In  cases 
where  this  object  is  not  sought,  panels  of  much  larger  size  may 
be  used.  Working  with  panels  2*4  x  I2J^  ft.  of  2-in.  plank  it 
was  found  that  each  panel  could  be  used  16  times  before  be- 
coming unfit  for  further  use,  but  as,  owing  to  the  nicety  of 
molded  surface  demanded,  panels  were  discarded  when  show- 
ing comparatively  small  blemishes,  this  record  cannot  be  taken 
as  a  true  indication  of  the  life  of  such  forms.  These  panel 
forms  are  used  by  the  railway  named  for  long  abutments  and 
piers  as  well  as  for  retaining  walls. 

A  different  type  of  sectional  form  construction  is  illustrated 
by  Figs.  101  and  102.  It  has  been  extensively  used  for  retain- 
ing wall  work  by  the  Chicago,  Burlington  &  Quincy  R.  R. 
The  studding  and  waling  are  framed  in  units  as  shown.  The 
lagging  is  framed  in  panels  for  the  rear  of  the  wall,  for  the 
face  of  the  coping,  and  for  the  inclined  toe  of  the  wall,  and  is 
ordinary  sheathing  boards  for  the  main  face  of  the  wall.  The 
make-up  of  the  several  panels  is  shown  by  the  drawings.  The 
reason  for  using  ordinary  sheathing  instead  of  panels  for  the 
face  of  the  wall  is  stated  by  Mr.  L.  ].  Hotchkiss,  Assistant 
Bridge  Engineer,  to  be  that  "the  sections  become  battered  and 
warped  with  use,  do  not  fit  closely  together,  and  leave  the  wall 
rough  when  they  are  removed."  The  manner  of  bracing  the 
form  and  of  anchoring  it  down  against  the  up-thrust  of  the 
wet  concrete  is  shown  by  Fig.  102. 


RETAINING   WALLS. 


263 


Two  other  examples  of  sectional  form  construction  are 
given  in  the  succeeding  descriptions  of  work  for  the  Grand 
Central  Station  terminal  in  New  York  City  and  for  the  Chi- 
cago Drainage  Canal.  In  the  former  work  it  is  notable  that 
panels  51x20  ft.  were  used,  being  handled  by  locomotive 
crane.  The  panels  used  on  the  drainage  canal  work  and  in  the 
forms  previously  described  are  of  sizes  that  can  be 
taken  down  and  erected  by  hand,  and  the  means  of  handling 
them  should  always  be  given  consideration  in  deciding  on  the 
sizes  to  be  adopted  for  form  panels  not  only  in  wall  construc- 
tion but  in  any  other  class  of  work  where  sectional  forms  may 


Cross  Section  Rear    Elevation. 

'  // 

Fig.    101.— Forms   for  Retaining-  Wall   Work,    C.,    B.    &   Q.   R.   R. 

be  used.  Wet  spruce  'or  yellow  pine  will  weigh  4^/2  Ibs.  per  ft. 
B.  M.,  so  that  a  panel  10  x  2^2  ft.  made  of  2-in.  plank  and  three 
2x4-in.  battens  will  weigh  some  225  Ibs.  In  form  work 
where  the  panels  are  removed  and  re-erected  in  succession 
facility  in  handling  is  an  important  matter.  When  one  figures 
that  he  may  handle  both  the  concrete  and  the  form  panels 
with  it  a  cableway  or  a  locomotive  crane  becomes  a  tool  well 
worth  considering  in  heavy  wall  work. 

Three  details  in  retaining  wall  form  work  that  are  often 
sources  of  annoyance  out  of  proportion  to  their  magnitude  are 
alignment,  coping  construction  and  wall  ties.  Small  varia- 
tions from  line  in  the  face  of  the  wall  are  seldom  noticeable, 


264 


CONCRETE    CONSTRUCTION. 


but  a  wavy  coping  shows  at  a  glance.  For  this  reason  it  is 
often  wise  to  build  the  coping  after  the  main  body  of  the  wall 
has  been  stripped,  or  if  both  are  built  together  to  provide  in 
the  forms  some  independent  means  of  Kning  up  the  coping 
molds.  In  the  form  shown  by  Fig.  101  the  latter  is  done  by 
bracing  the  coping  panel  so  as  to  permit  it  to  be  set  and  lined 
up  independently  of  the  main  form.  A  separate  form  for  mold- 
ing the  coping  after  the  main  body  of  the  wall  is  completed 
may  be  constructed  as  shown  by  Fig.  103.  Bolts  at  B  and  C 
permit  the  yokes  to  be  collapsed  and  the  form  to  be  shifted 


Fig.    102. — Sketch    Showing    Method    of    Bracing    Form    Shown    by    Fig.    101. 

ahead  as  the  work  advances.  This  mold  provides  for  beveling 
the  top  edges  of  the  coping  and  also  the  edge  of  the  overhang, 
and  the  beveling  or  rounding  of  these  edges  should  never  be 
omitted  where  a-  neat  appearance  is  desired.  It  is  not  essen- 
tial, however,  that  this  finishing  be  done  in  the  molds.  By 
stripping  the  concrete  while  it  is  still  pliable  the  edges  can  be 
worked  down  by  the  ordinary  cement  sidewalk  edger. 

Wall  ties  are  commonly  used  to  hold  the  face  and  back 
forms  to  proper  spacing,  but  occasionally  they  are  not  per- 
mitted. In  the  latter  case  the  bracing  must  be  arranged  to 


RETAINING  WALLS. 


265 


hold  the  forms  from  tipping  inward  as  well  as  from  being 
thrust  outward.  A  good  arrangement  is  that  shown  by  Fig. 
102.  In  fastening  the  forms  with  ties  the  choice  is  usually 
between  long  bolts  which  are  removed  when  the  molds  are 
taken  down  and  wire  ties  which  are  left  embedded  in  the  con- 
crete. The  selection  to  be  made  depends  upon  the  character 
of  the  work.  When  sectional  forms  are  used  like  the  one 
shown  by  Fig.  101,  for  long  stretches  of  wall  of  nearly  uni- 
form cross-section  bolts  are  generally  more  economical  and 
always  more  secure.  If  the  bolts  are  sleeved  with  scrap  gas 

Frames  6'0"  C.toC. 


Fig.   103.— Sectional  Form  for  Constructing  Coping. 

pipe  having  the  ends  corked  with  waste  the  bolts  can  be 
removed  ordinarily  without  difficulty.  To  make  the  pipe 
sleeve  serve  also  as  a  spacer  the  end  next  the  face  may  be 
capped  with  a  wooden  washer  which  is  removed  and  the  hole 
plastered  when  the  forms  are  taken  down.  With  bolt  ties  the 
forms  can  be  filled  to  a  depth  of  15  to  20  ft  with  sloppy  con- 
crete. This  is  hardly  safe  with  wire  ties  unless  more  wire  and 
better  tieing  are  employed  than  is  usual.  It  takes  four  strands 
of  No.  10  to  give  the  same  working  stress  as  a  J^-in.  threaded 
rod  and  the  tieing  in  of  four  strands  of  wire  so  that  they  will 


266  CONCRETE    CONSTRUCTION. 

be  without  slack  and  give  is  a  task  requiring  some  skill.  Bolts 
are  much  more  easily  placed  and  made  tight.  In  the  matter 
oC  cost  of  metal  left  in  the  wall,  the  question  is  between  the 
cost  of  scrap  gas  pipe  and  of  wire ;  the  pound  price  of  the 
wire  is  greater  but  fewer  pounds  are  used  and  the  metal  is  in 
more  convenient  shape  to  cut  to  length  and  to  handle.  This 
convenience  in  shaping  the  tie  to  the  work  gives  the  advan- 
tage to  wire  ties  for  isolated  jobs  or  jobs  which  involve  a  con- 
tinual change  in  the  length  and  spacing  of  the  ties.  In  general 
the  contractor  will  find  bolts  preferable  where  sectional  forms 
arc  used  and  wire  ties  preferable  when  using  continuous 
forms. 

One  objection  urged  against  the  use  of  wire  ties  is  that  the 
metal  is  exposed  at  the  face  of  the  work  when  they  are  clipped 
off  unless  the  concrete  is  chipped  and  the  cavity  plastered. 
To  obviate  this  objection  various  forms  of  removable  "heads" 
have  been  devised.  Two  such  devices  are  shown  by  Figs.  104 


Fig.  104.— Tie  for  Wall  Forms.  Fig.    105.— Tie   for   Wall   Forms. 

and  105.  In  both  the  bolt  is  unscrewed,  leaving  the  "heads" 
embedded.  The  head  shown  by  Fig.  104  has  the  advantage 
that  it  can  be  made  by  any  blacksmith,  while  the  head  shown 
by  Fig.  105  is  a  special  casting. 

MIXING  AND  PLACING  CONCRETE.— Where  a  long 
stretch  of  wall  is  to  be  built  the  system  of  mixing  and  handling 
the  concrete  must  be  capable  of  being  shifted  along  the  work. 
For  isolated  walls  of  short  length  this  problem  is  a  simpler 
one.  Where  the  mixer  can  be  installed  on  the  bank  above, 
wheeling  to  chutes  reaching  down  to  the  work  is  the  best  solu- 
tion. As  shown  in  Chapter  IV  concrete  can  be  successfully 
and  economically  chuted  to  place  to  a  greater  extent  than 
most  contractors  realize.  Where  the  mixer  has  to  be  installed 
at  the  foot  of  the  wall  wheelbarrow  inclines,  derricks,  gallows 
frames,  etc.,  suggest  themselves  as  means  of  handling  the  con- 
crete. It  is  not  this  class  of  work,  however,  but  the  long 


RETAINING   WALLS.  267 

stretches  of  heavy  section  walls  such  as  occur  in  depressed  or 
elevated  railway  work  in  cities  that  call  for  thought  in  the 
arrangement  and  selection  of  mixing  and  handling  plant. 

In  building  the  many  miles  of  retaining  wall  in  the  work  of 
doing  away  with  grade  crossings  in  Chicago,  111.,  trains  made 
up  of  a  mixer  car  and  several  material  cars  have  been  used. 
The  mixer  is  mounted  on  a  flat  car  set.  at  the  head  of  the 
train  and  is  covered  by  a  decking  carrying  two  charg- 
ing hoppers  set  above  the  mixer.  The  material  cars  are 
arranged  behind,  the  sand  and  stone  or  gravel  being  in  gon- 
dola cars.  Portable  brackets  hooked  to  the  sides  of  the 
gondola  cars  carry  runways  for  wheelbarrows.  Sand  and 
stone  or  gravel  are  wheeled  to  the  charging  hoppers,  the  work 
being  continuous  since  one  hopper  is  being  filled  while  the 
other  is  being  discharged  into  the  mixer.  The  mixer  dis- 
charges either  into  a  chute,  wheelbarrows  or  buckets.  The 
foregoing  is  the  general  arrangement ;  it  is  modified  in  special 
instances,  as  is  mentioned  further  on.  The  chief  objection  to 
the  method  is  the  difficulty  of  loading  the  wheelbarrows  stand- 
ing on  runways  level  with  the  tops  of  the  gondola  sides.  The 
lift  from  the  bottom  of  the  car  is  excessive,  and  as  pointed  out 
previously,  shoveling  stone  or  gravel  by  digging  into  it  from 
the  top  is  a  difficult  task. 

The  delivery  of  the  concrete  into  the  fojms  was  accom- 
plished by  chute  where  possible,  otherwise  by  wheelbarrows 
or  cranes,  and  in  one  case  by  belt  conveyor.  In  the  last  in- 
stance the  mixer  car  was  equipped  with  a  Drake  continuous 
mixer  and  was  set  in  front.  Behind  it  came  three  or  four 
gondola  cars  of  sand  and  stone,  and  at  the  rear  end  a  box  car 
of  cement.  All  material  was  wheeled  on  side  runways  to  two 
charging  hoppers  over  the  mixer.  The  mixer  discharged  onto 
a  belt  conveyor  carried  by  a  25-ft.  boom  guyed  to  an  A-frame 
on  the  car  and  pivoted  at  the  car  end  to  swing  180°  by  means 
of  a  tag  line.  The  outer  end  of  the  conveyor  was  swung  over 
the  forms.  A  2^-in.  wire  rope  wrapped  eight  times  around 
two  drums  on  the  mixer  car  and  passing  through  slots  in  the 
floor  to  anchors  placed  one  500  ft.  in  front  and  one  500  it. 
to  the  rear  enabled  the  train  to  be  moved  back  and  forth 
along  the  work.  This  scheme  of  self-propulsion  saved  the  hire 
of  a  locomotive.  In  another  case  the  mixer  was  discharged 


268 


CONCRETE    CONSTRUCTION. 


into  buckets  which  were  handled  by  a  crane  traveling  back 
and  forth  along  a  track  laid  on  two  flat  cars. 

Another  type  of  movable  mixer  plant  used  in  constructing 
a  sea-wall  some  3^  miles  long  at  Galveston,  Tex.,  is  shown  by 


Fig.    1C8.— Side    Elevation    of    Traveling    Mixer    Plant,    Galveston    Sea    Wall. 

Figs.  106  and  107.  Two  of  these  machines  mixed  and  placed 
some  127,000  cu.  yds.  of  concrete,  in  i  cu.  yd.  batches.  Two 
I2-HP.  engines  operated  the  derricks  and  one  i6-HP.  engine 
operated  the  Smith  mixer;  all  engines  took  steam  from  a 


Fig.  107.— End  Elevation  of  Traveling  Mixer,  Galveston  Sea  Wall. 

5O-HP.  boiler.  The  rated  capacity  of  each  machine  was  300  to 
350  cu.  yds.  per  day.  The  method  of  operation  is  clearly  indi- 
cated by  the  drawings. 


RETAINING   WALLS.  269 

Placing  the  concrete  in  the  forms  is  generally  required  to  be 
done  in  layers ;  with  wet  mixtures  this  means  little  more  than 
distributing  the  concrete  somewhat  evenly  along  the  wall  and 
slicing  and  puddling  it  to  get  rid  of  air  and  prevent  segre- 
gation. Where  mortar  facing  is  required  the  face  form  de- 
scribed in  Chapter  VIII  may  be  used.  A  reasonably  good 
surface  can  be  secured  without  mortar  facing  by  spading  the 
face.  With  dry  concrete,  placing  and  ramming  in  layers,  calls 
for  such  care  as  is  necessary  in  dry  concrete  work  everywhere. 
Where  new  concrete  has  to  be  placed  on  concrete  placed  the 
day  before,  good  bond  may  be  secured  and  the  chance  of 
efflorescence  be  reduced  by  the  methods  described  in  Chap- 
ter VIII. 

WALLS  IN  TRENCH.— In  canal  excavation,  in  subway 
work  in  cities,  and  the  like,  it  is  often  necessary  to  dig 
trenches  and  build  retaining  walls  in  them  before  excavating 
the  core  of  earth  between  the  walls.  The  following  examples 
of  such  work  are  taken  from  personal  records : 

Example  I. — A  Smith  mixer  was  used,  the  concrete  being 
delivered  where  wanted  by  a  Lambert  cableway  of  400  ft. 
span.  The  broken  stone  and  sand  were  delivered  near  the 
work  in  hopper-bottom  cars  which  were  dumped  through  a 
trestle  onto  a  plank  floor.  Men  loaded  the  material  into  one- 
horse  dump  carts  which  hauled  it  900  ft.  to  the  mixer  platform. 
This  platform  was  24  x  24  ft.  square,  and  5  ft.  high,  with  a 
planked  approach  40  ft.  long  and  contained  7,500  ft.  B.  M. 
The  stone  and  sand  were  dumped  at  the  mouth  of  the  mixer 
and  shoveled  in  by  4  men.  Eight  men,  working  in  pairs, 
loaded  the  broken  stone  into  the  carts,  and  2  men  loaded  the 
sand.  Each  cart  was  loaded  with  about  70  shovelfuls  of  stone 
on  top  of  which  35  shovelfuls  of  sand  were  thrown.  It  took 
3  to  5  minutes  to  load  on  the  stone  and  I  minute  to  load  the 
sand.  The  carts  traveled  very  slowly,  about  150  ft.  a  minute- 
in  fact,  all  the  men  on  the  job,  including  the  cart  drivers,  were 
slow.  After  mixing,  the  concrete  was  dumped  into  iron 
buckets  holding  14  cu.  ft.  water  measure,  making  about  l/2  cu. 
yd.  in  a  batch.  The  buckets  were  hooked  on  to  the  cableway 
and  conveyed  where  wanted  in  the  wall.  Steam  for  running 
the  mixer  was  taken  from  the  same  boiler  that  supplied  the 
cableway  engine.  The  average  output  of  this  plant  was  100 


270  CONCRETE    CONSTRUCTION. 

cu.  yds.  of  concrete  per  lo-hour  day,  although  on  many  days 
the  output  was  125  cu.  yds.,  or  250  batches.  The  cost  of 
mixing  and  placing  was  as  follows,  on  a  basis  of  100  cu.  yds. 
per  day: 

Per  day.         Per  cu.  yd. 

8  men  loading  stone  into  carts $12.00  $  .12 

2  men  loading  sand  into  carts 3.00  .03 

i  cart   hauling  cement 3.00      ,  .03 

8  carts  hauling  stone  and  sand 24.00  .24 

4  men  loading  mixer 6.00  .06 

1  man  dumping  mixer 1.50  .01 

2  men  handling  buckets  at  mixer.  .  .  .        3.00  .03 
6  men  dumping  buckets  and  ramming       9.00  .09 

12  men  making  forms  at  $2.50 30.00  .30 

i  cable  engineman 3.00  .03 

I   fireman    2.00  .02 

i  foreman   6.00  .06 

i  water-boy    i.oo  .01 

i  ton  coal  for  cableway  and  mixer.  . .  .       4.00  .04 


Total    $107.50  $1.07 

In  addition  to  this  cost  of  $1.07  per  cu.  yd.  there  was  the 
cost  of  moving  the  whole  plant  for  every  350  ft.  of  wall.  This 
required  2  days,  at  a  cost  of  $100,  and  as  there  were  about 
1,000  cu.  yds.  of  concrete  in  350  ft.  of  wall  16  ft.  high,  the  cost 
of  moving  the  plant  was  10  cts.  per  cu.  yd.  of  concrete,  bring- 
ing the  total  cost  of  mixing  and  placing  up  to  $1.17  per  cu. 
yd.  As  above  stated,  the  whole  gang  was  slow. 

The  labor  cost  of  making  the  forms  was  high,  for  such 
simple  and  heavy  work,  costing  $10  per  M.  of  lumber  placed 
each  day.  The  forms  were  2-in.  sheeting  plank  held  by 
4'x6-in.  upright  studs  2V2  ft.  apart,  which  were  braced  against 
the  sides  of  the  trench.  The  face  of  the  forms  was  dressed 
lumber  and  all  cracks  were  carefully  puttied  and  sandpapered. 

The  above  costs  relate  only  to  the  massive  part  of  the  wall 
and  not  the  cost  of  putting  in  the  facing  mortar,  which  was 
excessively  high.  The  face  mortar  was  2  ins.  thick,  and  about 
3*'2  cu.  yds.  of  it  were  placed  each  day  with  a  force  of  8  men ! 
Two  of  these  men  mixed  the  mortar,  2  men  wheeled  it  in  bar- 


RETAINING   WALLS.  271 

rows  to  the  wall,  2  men  lowerea  it  in  buckets,  and  2  men  put 
it  in  place  on  the  face  of  the  wall.  If  we  distribute  this  labor 
cost  on  the  face  mortar  over  the  100  cu.  yds.  of  concrete  laid 
each  day,  we  have  another  12  cts.  per  cu.  yd. ;  but  a  better 
way  is  to  regard  this  work  as  a  separate  item,  and  estimate  it 
as  square  feet  of  facing  work.  In  that  case  these  8  men  did 
500  sq.  ft.  of  facing  work  per  day  at  a  cost  of  nearly  2^2  cts. 
per  sq.  ft.  for  labor. 

Example  II. — The  building  of  a  wall  similar  to  the  one  just 
described  was  done  by  another  gang  as  follows:  The  stone 
and  sand  were  delivered  in  flat  cars  provided  with  side  boards. 
In  a  stone  car  5  men  were  kept  busy  shoveling  stone  into  iron 
dump  buckets  having  a  capacity  of  20  cu.  ft.  water  measure. 
Each  bucket  was  filled  about  two-thirds  full  of  stone,  then  it 
was  picked  up  by  a  derrick  and  swung  over  to  the  next  car 
which  contained  sand,  where  two  men  filled  the  remaining 
third  of  the  bucket  with  sand.  The  bucket  was  then  lifted 
and  swung  by  the  derrick  over  to  the  platform  of  the  mixer 
where  it  was  dumped  and  its  contents  shoveled  by  four  men 
into  the  mixer,  cement  being  added  by  these  men.  The  mixer 
was  dumped  by  two  men,  loading  iron  buckets  holding  about 
l/2  cu.  yd.  of  concrete  each,  which  was  the  size  of  each  batch. 
A  second  derrick  picked  up  the  concrete  bucket  and  swung  it 
over  to  a  platform  where  it  was  dumped  by  one  man  ;  then  ten 
men  loaded  the  concrete  into  wheelbarrows  and  wheeled  it 
along  a  runway  to  the  wall.  One  man  assisted  each  barrow  in 
clumping  into  a  hopper  on  the  top  of  a  sheet-iron  pipe  which 
delivered  the  concrete.  The  two  derricks  were  stiff-leg  der- 
ricks with  4O-ft.  booms,  provided  with  bull-wheels,  and  oper- 
ated by  double  cylinder  (7  x  lo-in.)  engines  of  i8-HP.  each. 
About  i  ton  of  coal  was  burned  daily  under  the  boiler  supply- 
ing steam  to  these  two  hoisting  engines.  The  output  of  this 
plant  was  200  batches  or  100  cu.  yds.  of  concrete  per  lo-hr. 
day,  when  materials  were  promptly  supplied  by  the  railroad ; 
but  delays  in  delivering  cars  ran  the  average  output  down  to 
80  cu.  yds.  per  day. 

On  the  basis  of  100  cu.  yds.  daily  output,  the  cost  of  mixing 
and  placing  the  concrete  was  as  follows : 


272  CONCRETE    CONSTRUCTION. 

Per  day.          Per  cu.  yd, 

5  men  loading  stone   $  7.50  $  .07^ 

2  men  loading  sand    3.00  .03 

4  men  charging  mixer 6.00  .06 

2  men  loading  concrete  into  buckets.       3.00  .03 

I  man  dumping  concrete  from  buckets       1.50  .01^ 

10  men  loading  and  wheeling  concrete     15.00  .15 

1  man  dumping  wheelbarrows '. .        1.50 

3  men  spreading  and  ramming 4.50 

2  enginemen    5.00  .05 

I  fireman    2.00  .02 

I  water-boy   i.oo  .01 

I  foreman    6.00  .06 

10  men  making  forms 25.00  .25 

I  ton  coal 4.00  .04 


Total 85.00  $  .85 

In  addition  there  were  8  men  engaged  in  mixing  and  plac- 
ing the  2-in.  facing  of  mortar  as  stated  above. 

CHICAGO  DRAINAGE  CANAL.— The  method  and  cost 
of  constructing  some  20,000  ft.  of  concrete  wall  by  contract  in 
building  the  Chicago  Drainage  Canal  is  compiled  from  records 
kept  by  Mr.  James  W.  Beardsley.  The  work  was  done  on  tw'o 
separate  sections,  Section  14  and  Section  15.  In  both  cases 
a  i-i 3/2-4  natural  cement  concrete  was  used  with  a  3~in.  facing 
and  a  3-in.  coping  of  1-3  Portland  cement  mortar. 

Section  14. — The  average  height  of  the  wall  was  10  ft.,  and 
the  thickness  at  base  was  one-half  the  height.  The  stone  for 
the  concrete  was  obtained  from  the  spoil  bank  of  the  canal, 
loaded  into  wheelbarrows  and  wheeled  about  100  ft.  to  the 
crusher;  some  was  hauled  in  wagons.  An  Austin  jaw  crusher 
was  used,  and  it  discharged  the  stone  into  bins  from  which 
it  was  fed  into  a  Sooysmith  mixer.  The  crusher  and  the  mixer 
were  mounted  on  a  flat  car.  Bucket  elevators  were  used  to 
raise  the  stone,  sand  and  cement  from  their  bins  to  the  mixer ; 
the  buckets  were  made  of  such  size  as  to  give  the  proper  pro- 
portions of  ingredients,  as  they  all  traveled  at  the  same  speed. 
Only  two  laborers  were  required  to  look  after  the  elevators. 
The  sand  and  cement  were  hauled  by  teams  and  dumped  into 


REGAINING   WALLS. 


273 


the  receiving  bins.    There  were  23,568  cu.  yds.  on  Section  14, 
and  the  cost  was  as  follows : 

Typical      Wages  per         Cost  per 

General  force :                             force.             10  hrs.  cu.  yd 

Superintendent    .  „ i.o  $5«oo  $0.026 

Blacksmith    i.i  2.75  0.016 

Timekeeper    0.5  2.50  0.007 

Watchman    0.6  2.00  0.007 

Water-boys   3.9  i.oo  0.022 

Wall  force : 

Foreman    0.9  2.50  0.013 

Laborers    8.6  1.50  0.073 

Tampers    2.3  1.75  0.022 

Mixer  force : 

Foreman    1.2  2.50  0.017 

Enginemen 1.8  2.50  0.025 

Laborers    6.7  1.50  0.057 

Pump  runner   i.o  2.00  o.oio 

Mixing  machines 1.7  1.25  0.012 

Timber  force : 

Foreman 0.6  2.50  0.008 

Carpenters    4.7  2.50  0.057 

Laborers 1.2  1.50  o.oio 

Helpers    5.3  2.50  0.075 

Hauling  force. 

Laborers    2.6  1.75  0.026 

Teams    6.3  3.25  0.116 

Crushing  force : 

Foreman    0.5  2.50  0.007 

Engineman    1.7  2.50  0.023 

Laborers    3.5  1.50  0.032 

Austin  crushers 1.7  1.20  o.on 

Loading  stone : 

Foreman    1.7  2.50  0.023 

Laborers    32.9  1.50  0.280 

Total  for  crushing,  mixing  and  placing $0.975 


274 


CONCRETE    CONSTRUCTION. 


The  daily  costs  charged  to  the  mixers  and  crushers  include 
the  cost  of  coal,  at  $2  a  ton,  and  the  cost  of  oil. 

The  gang-  "loading  stone"  apparently  did  a  good  deal  of 
sledging  of  large  stones,  and  they  also  wheeled  a  large  part  of 
it  in  barrows  to  the  crusher. 

The  plant,  cost  $9,600,  distributed  as  follows : 

2  jaw   crushers    $3,ooo 

2  mixers 3,ooo 

Track    1,260 

Lumber    500 

Pipe 840 

Sheds 400 

Pumps 600 

Total    $9,600 

If  this  first  cost  of  the  plant  were  distributed  over  the 
23,568  cu.  yds.  of  concrete  it  would  amount  to  41  cts.  per 
cu.  yd. 

The  cost  of  the  concrete  was  as  follows : 

Per  cu.  yd. 

Utica  cement,  at  $0.65  per  bbl $0.863 

Portland  cement,  at  $2.25  per  bbl 0.305 

Sand,  at  $1.35  per  cu.  yd 0.465 

Stone  and  labor,  as  above  given - 0.975 

Total  $2.608 

First  cost  of  plant $0.407 

Section  15. — The  conditions  on  this  section  were  much  the 
same  as  on  Section  14,  just  described,  except  that  the  lime- 
stone was  quarried  from  the  bed  of  the  canal,  and  was  crushed 
in  a  stationary  crusher,  No.  7  Gates.  The  stone  was  hauled 
1 ,000  ft.  to  the  crusher  on  cars  drawn  by  a  cable  from  a  hoist- 
ing engine.  The  output  of  this  crusher  averaged  210  cu.  yds. 
per  day  of  10  hrs.  The  crushed  stone  was  hauled  in  dump 
cars,  drawn  by  a  locomotive,  to  the  mixers.  Spiral  screw 
mixers  mounted  on  flat  cars  were  used,  and  they  delivered  the 
concrete  to  belt  conveyors  which  delivered  'he  concrete  into 
the  forms. 

The  forms  on  Section  15  (and  on  Section  14  as  well)  con- 
sisted of  upright  posts  set  8  ft.  apart  and  9  ins.  in  front  of  the 


RETAINING    WALLS. 


275 


wall,  held  at  the  toe  by  iron  dowels  driven  into  holes  in  the 
rock,  and  held  to  the  rear  posts  by  tie  rods.  The  plank  sheet- 
ing was  made  up  in  panels  2  ft.  wide  and  16  ft.  long,  and  was 
held  up  temporarily  by  loose  rings  which  passed  around  the 
posts  which  were  gripped  by  the  friction  of  the  rings.  These 
panels  were  brought  to  proper  line  and  held  in  place  by 
wooden  wedges.  After  the  concrete  had  set  24  hrs.  the 
wedges  were  struck,  the  panels  removed  and  scraped  clean 
ready  to  be  used  again. 

The  cost  of  quarrying  and  crushing  the  stone,  and  mixing 
the  concrete  on  Section  15  was  as  follows: 

Typical  Wages  per  Cost  per 

General  force —                           force.           10  hrs.  cu.  yd. 

Superintendent    i.o               $5-OO  $0.024 

Blacksmith    0.9                 2.75  o.oi  i 

Teams   1.7                 3.00  0.025 

Waterboy    4.5                 i.oo  0.022 

Wall  force- 
Foreman    i.i  2.50  o.oio 

Laborers    14.4  1.50  0.105 

Tampers   o.i  1.75  o.ooi 

Mixer  force — 

Foreman   ^ 2.1  2.50  0.026 

Enginemen    2.1  2.50  0.022 

Laborers    23.1  1.50  0.180 

Mixing  machines 2.1  1.25  0.022 

Timber  force — 

Carpenters    0.8  3.00  0.013 

Laborers    0.7  1.50  0.005 

Helpers    10.2  2.50  0.125 

Hauling  force — 

Foreman    0.7  2.50  0.009 

Enginemen    ...... 1.4  2.50  0.019 

Fireman   0.4  1.75  0.003 

Brakeman 2.2  2.00  0.018 

Teams   0.4  3.25  0.007 

Laborers    1.5  1.50  o.oio 

Locomotives    1.4  2.25  0.015 


276  CONCRETE    CONSTRUCTION. 

Crushing  force — 

Foreman 1.0               2.50  0.014 

Enginemen I.O                2.50  0.014 

Laborers    H.l                1.50  0.081 

Firemen    I.O                175  0.008 

Gyratory  crusher I.O                2.25  o.on 

Quarry  force — 

Foreman    1.2                 2.50  0.012 

Laborers    19.0                1.50  0.140 

Drillers   1.8                 2.OO  0.017 

Drill  helpers   1.8                 1.50  0.013 

Machine  drills   1.8                1.25  o.oi  i 

Total $0.993 

The  first  cost  of  the  plant  for  this  work  on  Section  15  was 
$25,420,  distributed  as  follows: 

i  crusher,  No.  7  Gates $12,000 

Use   of  locomotive 2,200 

Car   and   track * 5>3OO 

3  mixers  3,ooo 

Lumber    i  ,200 

Pipe    720 

Small  tools   i  ,000 


Total * $25,420 

This  $25,420  distributed  over  the  44,811  cu.  yds.  of  concrete 
amounts  to  57  cts.  per  cu.  yd. 

It  will  be  noted  that  2  mixers  were  kept  busy.  Their  aver- 
age output  was  loo  cu.  yds.  each  per  day,  which  is  the  same 
as  for  the  mixers  on  Section  14. 

The  total  cost  of  concrete  on  Section  15  was  as  follows: 

Per  cu.  yd. 

Labor  quarrying,  crushing  and  mixing $0.991 

Explosives    0.083 

Utica  cement,  at  $0.60  per  bbl 0.930 

Portland  cement,  at  $2.25  per  bbl 0.180 

Sand,  at  $1.35  per  cu.  yd 0.476 


RETAINING   WALLS. 


277 


It  is  not  strictly  correct  to  charge  the  full  first  cost  of  the 
plant  to  the  work  as  it  possessed  considerable  salvage  value 
at  the  end. 

Comparison. — For  the  purpose  of  comparing  Sections  14 
and  15  the  following  summary  is  given  of  the  cost  per  cubic 
yard  of  concrete: 

Sec.  14.  Sec.  15. 

General  force $0.078  $0.082 

Wall  force   0.108  0.116 

Mixing  force   0.121  0-250 

Timbering  force    o^S0.  0.140 

Hauling  force   .  . .  . 0.142  0.081 

Crushing  force    0.073  0.128 

Quarry  force   0.303  0.275 

Cement,  natural    0.863  °-93° 

Cement,  Portland 0.305  0.180 

Sand   0.465  0.476 

Plant    (full   cost) 0.407  0.567 


Total    $3.015  $3.225 

It  should  be  remembered  that  on  Section  14  there  was  no 
drilling  and  blasting  of  the  rock,  but  that  the  "quarry  force" 
not  only  loaded  but  hauled  the  stone  to  the  crusher.  The 
cost  of  mixing  on  Section  15  is  higher  than  on  Section  14  be- 
cause the  materials  were  dumped  on  platforms  and  shoveled 
into  the  mixer,  instead  of  being  discharged  from  bins  into  the 
mixer  as  on  Section  14. 

GRAND  CENTRAL  TERMINAL,  NEW  YORK,  N.  Y.— 
In  building  a  retaining  wall  of  the  cross-section,  shown  in  Fig. 
108,  a  traveling  tower  moving  on  tracks  parallel  to  the  wall 
contained  the  concrete  mixing  plant.  The  construction  of  the 
tower  is  shown  in  Fig.  109.  The  tower  had  two  platforms, 
one  at  the  top  carrying  two  lo-cu.  yd.  bins  for  sand  and  stone 
and  the  other  directly  below  carrying  40  cu.  ft.  (4  cu.  ft.  ce- 
ment, 12  cu.  ft.  sand  and  24  cu.  ft.  stone)  Ransome  .mixer 
driven  by  a  30  H.P.  motor  and  a  Lidgerwood  motor  hoist. 
The  elevator  tower  carried  two  4O-cu.  ft.  Ransome  dumping 
buckets  traveling  in  guides  and  dumping  automatically  into 
the  bins.  These  buckets  were  operated  by  the  Lidgerwood 
motor  hoist  on  the  mixer  platform.  Sand  and  broken  stone 


278 


CONCRETE    CONSTRUCTION. 


on  flat  cars  were  brought  alongside  the  tower.  The  sand  was 
shoveled  direct  from  the  car  into  the  sand  bucket,  but  the 
broken  stone  was  shoveled  into  wheelbarrows  which  were 
wheeled  over  a  light  bridging  from  car  to  bucket  and  dumped. 
Wheelbarrows  were  used  for  handling  the  stone  chiefly  be- 
cause the  capacity  of  the  plant  was  so  great  that  enough  men 
could  not  be  worked  in  the  limited  space  around  the  bucket  to 
keep  up  the  supply  by  shoveling.  The  wheelbarrow  work 


Weep  Hole, 
JO'O^C.+oC. 


Fig. 


_ 
~Eartti~or  soft  ffcc/r 


lOS.^Cross    Section    of    Retaining   Wall,    New 

Work. 


York    Central    Terminal 


added  materially  to  the  cost.  Cement  was  carried  from  the 
cars  to  the  sand  bucket,  hoisted  and  stored  on  the  mixer  plat- 
form which  provided  storage  room  for  100  bags.  A  1-3-6  mix- 
ture was  used ;  the  sand  and  stone  were  chuted  directly  from 
the  bins  to  the  charging  hopper  and  the  cement  was  charged 
by  hand.  The  mixed  concrete  was  delivered  to  two  I  cu.  yd. 
dump  cars  running  on  a  2-ft.  gage  track  laid  in  sections  on  the 


Fig.  109.— Portable  Concrete  Mixing  Tower,  N.  Y.  Central  Terminal  Work. 

279 


280 


CONCRETE    CONSTRUCTION. 


cross  pieces  connecting  the  uprights  of  the  forms.  The  track 
had  no  switches,  so  that  one  car  had  to  wait  for  the  other. 
Four  men  were  required  to  push  each  car  and  two  more  men 
assisted  in  dumping  the  car  and  kept  the  track  clear.  The 
wall  was  built  in  sections  51  ft.  long,  each  containing  250  cu. 
yds.  One  of  these  sections  was  filled  in  8  hours  with  ease  and 
by  a  little  hustling  a  section  was  filled  in  6^4  hours,  which  is 
at  the  rate  of  37  cu.  yds.  of  concrete  per  hour.  Working  8 
hours  per  day  the  cost  of  mixing,  transporting  and  placing 
concrete  with  this  mixing  plant,  with  wages  for  common  labor 
of  $1.50  per  day,  was  as  follows : 

Total.      Per  cu.  yd. 
2  men   carrying  cement $     3.00  $0.012 

6  men  shoveling  sand .       9.00  0.036 

17  men  shoveling  stone 25.00  o.ioo 

1 1  men  wheeling  stone 16.00  0.064 

2  men  at  stone  and  sand  bins 3.00  0.012 

2  men  opening  cement  bags 3.00  0.012 

i  man  dumping  hopper 1.50  0.006 

i  man  dumping  mixer 1.50  0.006 

i  man  cleaning  chute,  mixer,  etc 1.50  0.006 

1  motorman  or  engineer 3.00  0.012 

\ 

Total  labor   mixing $  66.50  $0.266 

8  men  pushing  2  cars 12.00  0.048 

2  men  cleaning  track,  etc 3.00  0.012 

7  men  spading  concrete 10.50  0.042 

Total  labor  transporting,  placing.  .$  25.50  $0.102 

I  foreman    5.00  0.020 

Electricity  estimated  7.00  0.028 

Total  general '......$  12.00  $0.048 

Grand  total    $104.00  $0.416 

It  will  be  noted  that  the  cost  of  shoveling  and  wheeling  the 
broken  stone  amounts  to  16.4  cts.  per  cu.  yd.,  or  nearly  40  per 
cent,  of  the  total  cost  of  mixing  and  placing.  The  cost  of 
spading  the  concrete  is  also  high  for  a  sloppy  mixture,  but  is 
probably  accounted  for  by  the  fact  that  the  concrete  had  to 
be  spaded  so  as  to  have  2  or  3  ins.  of  clear  mortar  next  the 


RETAINING   WALLS.. 


281 


forms.  The  forms  used  in  constructing  the  wall  are  shown 
by  Figs,  no  and  in.  They  were  made  in  panels  51  ft.  long 
and  a  locomotive  crane  was  used  to  shift  the  panels.  This 
crane  worked  handling  forms  only  a  small  part  of  the  time, 
but  a  form  gang  of  IO  carpenters  was  kept  busy  all  of  the  time 
moving  and  reassembling.  Assuming  the  work  of  the  crane 


Fig.   110.— End  View   of  Forms   for  Retaining  Wall,   New  York  Central 
Terminal  Work. 


to  amount  to  $5  per  day  and  the  wages  of  the  carpenter  gang 
to  amount  to  $25,  we  get  a  cost  of  12  cts.  per  cubic  yard  of 
concrete  for  shifting  forms.  It  should  be  noted  carefully  that 
the  costs  given  for  this  work  do  not  include  cost  of  materials, 
interest  on  plant,  superintendence  and  other  items. 


282 


CONCRETE    CONSTRUCTION. 


WALL  FOR  RAILWAY  YARD.— For  building  a  retain- 
ing wall  7  ft.  high,  forms  were  made  and  placed  by  a  carpenter 
and  helper  at  $8  per  M.,  wages  being  35  cts.  and  20  cts.  an 
hour,  respectively.  Concrete  materials  were  dumped  from 
wagons  alongside  the  mixing  board.  Ramming  was  unusually 
thorough.  Foreman  expense  was  high,  due  to  small  number 
in  gang ;  2  cu.  yds.  were  laid  per  hour  by  the  gang. 


^4...^...4-//«-ir 

'plan  of  Corner  of  Forms. 

Fig.  111. — Corner  Detail  of  Retaining  Wall  Forms,   New  York  Central 
Terminal  Work. 

Per  day.  Per  cu.  yd. 

7  mixers,  15  cts.  per  hour '. $10.50  $0.53 

2  rammers,  15  cts.  per  hour 3.00  0.15 

i  foreman  30  cts.  per  hr.,  I  waterboy  5  cts.     3.50  0.17 

Total  labor $17.00  $0.85 

The  total  cost  was  as  follows  per  cubic  yard : 

Per  cu.  yd. 

0.8  bbls.  Portland  cement,  at  $2 $1.60 

Sand    0.30 

Gravel    0.70 

Labor  mixing  and  placing 0.85 

Lumber  for  forms,  at  $16  per  M 0.56 

Labor  on  forms,  at  $8  per  M 0.28 

Total,  per  cubic  yard $4.29 

The  sheathing  plank  for  the  forms  was  2-in.  hemlock. 


RETAINING   WALLS.  283 

CONCRETE  FOOTING  FOR  RUBBLE  MASONRY 
RETAINING  WALL. — In  constructing  a  footing  for  a 
retaining  wall?  at  Grand  Rapids,  Mich.,  a  1-2^-5  natural 
cement  concrete  was  used.  It  was  found  that  I  cu.  yd.  of 
concrete  was  equivalent  to  29.8  cu.  ft.  of  material  composed 
of  3.6  cu.  ft.  or  i.i  bbls.  of  cement,  8.4  cu.  ft.  or  2.7  bbls.  of 
sand  and  17.8  cu.  ft.  or  5.5  bbl.  of  broken  stone.  The  labor 
cost  of  15.5  cu.  yds.  of  concrete  was  as  follows: 

Item.  Total.  Per  cu.  yd. 

Foreman,  14  hours  at  40  cts $  5.60  $0.3613 

Foreman,  20  hours  at  22.5  cts 4.50  0.2903 

Laborers,  49  hours  at  12.5  cts 6.11  0.3942 

Mason,  2  hours  at  35  cts 0.70  0.0451 


Total  labor $16.91  $1.0909 

All  material  was  furnished  by  the  railway  company,  the  con- 
tractor furnishing  labor  only;  his  contract  price  for  this  was 
$i  per  cu.  yd. 

TRACK  ELEVATION,  ALLEGHENY,  PA.— The  wall 
was  6,100  ft.  long  and  75  per  cent,  was  on  curves.  The  first 
wall  built  had  a  top  width  of  2l/2  ft.  and  a  bottom  width  of 
0.4  the  height  with  the  back  on  a  smooth  batter.  Later  the 
back  was  stepped  and  last  the  wall  was  proportioned  as  fol- 
lows :  Calling  the  height  from  top  of  foundation  to  under 
coping,  then  width  of  base  was  0.45  (/*  +  3),  the  top  measur- 
ing 2}/2  ft.  The  back  was  arranged  in  steps  24  ins.,  30  ins., 
and  36  ins.  high,  and  the  thickness  of  wall  at  each  step  was, 
calling  h  equal  to  height  of  step  from  base,  0.45  (/»  +  3).  Sev- 
eral forms  of  expansion  joints  were  tried.  The  first  was  tarred 
paper  extending  through  the  wall  every  50  ft. ;  the  second  was 
*/2-in.  boards  running  through  the  wall  every  50  ft. ;  the  third 
was  J/^-in.  board  extending  2  ft.  into  the  wall,  with  a  *4~in. 
cove  at  the  angles,  every  25  ft.  The  third  construction  gave 
perfect  satisfaction. 

A  1-2-5  natural  cement  and  a  1-3-6  Portland  cement  con- 
crete mixed  fairly  wet  were  used.  The  concrete  was  laid  in 
8-in.  courses  and  faced  with  a  1-2  mortar.  The  forms  were 
2-in.  white  pine  faced -and  jack  planed  on  the  edges;  upon 
removal  of  the  forms  board  marks  and  other  defects  were  re- 


284  CONCRETE    CONSTRUCTION. 

moved  and  a  wash  of  neat  cement  was  applied.  One  contrac- 
tor used  hand  mixing.  The  sand  and  gravel  were  measured 
in  wheelbarrows  and  wheeled  onto  the  platform ;  the  sand  and 
cement  were  spread  in  thin  layers,  one  over  the  other,  and 
thoroughly  mixed  dry ;  the  gravel  was  then  spread  over  the 
mixture,  the  whole  was  shoveled  into  barrows  or  the  pit  again 
shoveled  into  place  and  rammed.  The  other  contractor  used 
a  cubical  mixer.  A  charging  box  holding  ij4  cu.  yds.  and 
graduated  to  show  the  correct  proportions  of  sand  and  gravel 
was  rilled  by  shoveling;  cement  was  placed  on  top  and  the  box 
hoisted  and  dumped  into  .the  mixer.  A  barrel  holding  the  cor- 
rect amount  of  water  was  emptied  into  the  mixer  which  was 
turned  10  or  15  times  and  discharged  into  cars.  The  costs  of 
mixing  by  hand  and  by  machine  were  as  follows : 

Hand  mixing.  Total.      Per  cu.  yd. 

y2  foreman  at  $3 .$  1.50  $0.025 

3  men  wheeling  barrows  at  $1.50 4.50  °-O75 

10  men  wheeling  materials  at  $1.50 15.00  0.250 

3  men  mixing  sand  and  gravel  at  $1.50.  .  4.50  0.075 

6  men  mixing  concrete  at  $1.50 9.00  0.150 

I  man  sprinkling  at  $1.50 1.50  0.025 


Total    $36.00  $0.600 

The  output  of  the  hand  mixing  gang  was  60  cu.  yds.  per 
day. 

Machine  mixing.                                            Total.  Per  cu.  yd. 

i  foreman  at  $3.50 $  3.50  $0.035 

1  stationary  engineer  at  $3 3.00  0.030 

y2  foreman  at  $1.75 0.87  0.009 

15  men  loading  charging  bucket  at  $1.50.  .   22.50  0.225 

2  men  dumping  charging  bucket  at  $1.75.     3.50  0.035 

2  tagmen  at  $2,  y2  time 2.00  0.020 

i  man  at  trap  at  $2,  ]/2  time i.oo  o.oio 


Total    $36.37  $0.364 

The  output  of  the  cubical  mixer  was  100  cu.  yds.  per  day. 
The  costs  of  placing  concrete  in  the  forms  above  the  founda- 
tion by  hand  below  12  ft.,  and  by  cars  and  derricks  any  height, 
were  as  follows : 


RETAINING   WALLS. 


285 


By  hand  (barrows)  below  12  ft.  Total.      Per  cu.  yd. 

4  men  loading  concrete  at  $1.50 $  6.00  $0.100 

I  foreman  l/2  time  at  $3 1.50  0.025 

10  men  wheeling  at  $1.50 I5-OO  0.250 

1  man  scraping  barrows  at  $1.50 1.50  0.025 

2  men  placing  concrete  at  $1.50 3.00  0.050 

1  man  placing  mortar  face  at  $1.50 1.50  0.025 

2  men    mixing    and    carrying    mortar    at 

$1.50    3.00  0.050 

Total    $31-50  $0.525 

By  cars  and  derricks — 

1  horse  and  driver  at  $3 $  3.00  $0.030 

2  men  dumping  concrete  l/2  time  at  $1.50.      1.50    •  0.015 

1  fireman  l/2  time  at  $1.75 0.88  0.009 

3  tagmen  at  $1.50 4.50  0.045 

8  men  placing  and  ramming  cone,  at  $1.50.   12.00  0.120 

2  men  mixing  mortar  at  $1.50 3.00  0.030 

2  men  placing  mortar  at  $1.50 3.00  0.030 

2  men  carrying  mortar  at  $1.50 3.00  0.030 

i  foreman  at  $3 3.00  0.030 

1  stationary  engineer  at  $3 3.00  0.030 

2  men  attending  hook  at  $1.50 3.00  0.030 

Total .$39.88  $0.399 

The  costs  of  placing  concrete  in  the  foundations  were  as 

follows : 

By  hand —  Total.      Per  cu.  yd. 

i  foreman  y2  time  at  $3 $  1.50  $0.025 

4  men  shoveling  concrete  at  $1.50 6.00  o.ioo 

i   man  placing  concrete  at  $1.50 1.50  0.025 

i   man  ramming  concrete  at  $1.50 1.50  0.025 

Total    $10.50  $0.175 

By  machine — 

I  horse  and  driver  at  $3 $  3.00  $0.030 

3  men  pushing  and  unloading  car  at  $1.50.     4.50  0.045 

5  men  placing  and  ramming  at  $1.50 7-5°  o-°75 

1  foreman  at  $3 3.00  0.030 

2  men  dumping  mixer  at  $1.50 3.00  0.030 


Total    $21.00 


$0.210 


286  CONCRETE    CONSTRUCTION. 

COST  OF  RETAINING  WALL.— The  following  figures  of 

the  cost  of  a  concrete  retaining  wall  are  given,  by  C.  C.  Wil- 
liams : 

Cost  of  Material. 

»  Unit 

Kind  and  amount  of  material —                   Price.  Cost. 

Stone,   441    tons $  .70  $308.70 

Sand,  182.5  yds 55  100.37 

Cement,  536  bbls 85  453.60 


Total .$862.67 

Lumber  24  value $205.33 

Wheelbarrows,  £4  value,  6  at  $3.50 15-75 


Total    $221.08 

Excavation--- 

Labor,  4,002  h'ours  at  15  cts , $600.30 

Carts,  800  hours  at  i2}/2  cts 100.00 

Foreman,  460  hours  at  35  cts. 171.00 

Water-boy,  240  hours  at  10  cts 24.00 


Total   $895.30 

Concrete — 

Labor,  2,398  hours  at  15  cts $359-7° 

Foreman,  224  hours  at  35  cts 774° 


Total $437-io 

Handling  material — 

Unloading  cars,  380  hours  at  15  cts $  57.00 

Foreman,  40  hours  at  35  Us 14.00 


Total    $  71.00 

Forms — 
Carpenters,  997  hours  at  22^2  cts $224.33 

Work  to  support  bridge — 

Carpenters,  542  hours  at  22l/2  cts $121.95 

Labor,  458  hours  at- 15  cts 68.70 


Total , $190.65 


RETAINING   WALLS. 


287 


Superintendence  and  office- 
Superintendent,  30  hours  at  50  cts $15.00 

Office    20.00 


Total   ,-. $35.00 


Grand  total $2,937.13 

Proportional  costs —  Per 

Cent. 

Cost  Per  of 

Yard  of  Total 

Item.                                                        Cost.     Concrete.  Cost. 

Concrete  materials    ... , .$  862.67        $2.02  46.7 

Laying  concrete 437.10           1.03  23.4 

Lumber    205.33             48  H-3 

Building   forms 224.33             -53  12.3 

Handling  material .  .  . .  .       71.00             .17  03.8 

Wheelbarrows x5-75             -04  oi.o 

Supt,   etc 35.00             .07  01.5 

Total    ..„....., $1,851.18       $4.34  loo.oo 

Work  on  bridge 190.65 

Excavation    895.30 


$2,937-13 


CHAPTER  XIV. 

METHODS  AND  COST  OF  CONSTRUCTING  CON- 
CRETE FOUNDATIONS  FOR  PAVEMENTS. 

Contractor's  skill  or  want  of  skill  in  systematizing  and  man- 
aging labor  counts  as  high  in  street  work  as  in  any  class  of 
concrete  construction.  As  previously  demonstrated,  the  cost 
of  mixing  is  a  very  small  portion  of  the  labor  cost  of  concrete 
in  place;  the  costs  of  getting  the  materials  to  the  mixer  and 
the  mixed  concrete  to  the  work  are  the  big  items,  and  in  street 
work  the  opportunity  for  increasing  the  cost  of  these  items 
through  mismanagement  is  magnified  by  the  large  area  of 
operations  involved  per  cubic  yard  of  concrete  placed.  One 
cubic  yard  of  concrete  makes  6  sq.  yds.  of  6-in.  pavement 
foundations  and  100  cu.  yds.  of  concrete  make  a  6-in.  founda- 
tion for  300  ft.  of  3O-ft.  street,  while  4  to  5  cu.  yds.  will  build 
100  ft.  of  ordinary  curb  and  gutter.  Thus  the  haulage  per 
cubic  yard  is  considerable  at  best,  and  lack  of  plan  in  dis- 
tributing stock  piles  and  handling  the  concrete  can  easily  re- 
sult in  such  increased  haulage  expenses  as  to  change  a  pos- 
sible profit  into  a  certain  loss.  A  little  thought  and  skill  in 
planning  street  work  pays  a  good  profit. 

MIXTURES  EMPLOYED.— A  comparatively  lean  con- 
crete will  serve  for  pavement  foundations ;  mixtures  of  1-4-8 
Portland  cement  or  1-2-5  natural  cement  are  amply  good  and 
it  is  folly,  ordinarily,  to  employ  richer  mixtures.  Until  re- 
cently, natural  cement  has  been  used  almost  exclusively ;  a 
1-2-5  natural  cement  mixture  requires  about  1.15  bbls.  of  ce- 
ment per  cubic  yard  of  concrete.  A  1-4-8  Portland  cement 
mixture  requires  about  0.7  bbl.  of  cement  per  cubic  yard.  In 
the  opinion  of  the  authors  a  considerably  leaner  mixture  of 
Portland  concrete  is  sufficiently  good  when  it  is  well  mixed  in 
machine  mixers— for  a  6-in.,  foundation  0.5  bbl.  per  cu.  yd. 
The  mixtures  actually  employed  are  proportioned  about  as 
stated  and  their  cost,  or  that  of  any  other  common  mixture, 

288 


PAl/'EMENT  FOUNDATION. 


289 


may  easily  be  computed  from  Tables  XII  and  XIII,  giving  for 
different  mixtures  the  quantities  of  cement,  sand  and  stone 
per  cubic  yard  of  concrete ;  the  product  of  these  quantities  and 
the  local  prices  of  materials  in  the  stock  piles  gives  the  cost. 
When  the  concrete  is  mixed  by  hand  the  ordinary  labor  cost  of 
foundations  is  0.4  to  0.5  of  a  lo-hour  day's  wages  per  cubic 
yard  of  concrete;  occasionally  it  may  be  as  low  as  0.3  of  a 
day's  wages  where  two  mixing  gangs  are  worked  side  by  side 
under  different  foremen  and  with  an  exacting  contractor. 
Data  for  machine  mixing  are  too  few  to  permit  a  similar  gen- 
eral statement  for  machine  work,  but  in  one  case  coming 
under  the  authors'  observation,  the  cost  figured  out  to  a  little 
less  than  0.2  of  a  day's  wages  per  cubic  yard. 

DISTRIBUTION  OF  STOCK  PILES.— Assuming  a  30-1!. 
street  and  a  1-3-5  concrete  laid  6  ins.  thick,  the  quantities  of 
concrete  materials  required  per  lineal  foot  of  street  are :  Ce- 
ment 0.60  bbl.,  sand  0.27  cu.  yd.,  stone  0.44  cu.  yd.  The  stock 
piles  should  be  so  distributed  that  each  supplies  enough  mate- 
rials for  a  section  of  foundation  reaching  half  way  to  the  next 
adjacent  stock  pile  on  each  side,  and  they  should  not  contain 
more  or  less  material,  otherwise  a  surplus  remains  to  be 
cleaned  up  or  a  deficiency  to  be  supplied  by  borrowing  from 
another  pile.  A  little  care  will  ensure  the  proper  distribution 
and  it  is  well  paid  for  in  money  saved  by  not  rehandling  sur- 
plus or  borrowed  materials.  For  a  given  mixture  and  a  given 
width  and  thickness  of  foundation,  the  sizes  of  the  stock  piles 
are  determined  by  their  distance  apart  and  this  will  depend 
upon  whether  hand  or  machine  mixing  is  employed  and  upon 
the  means  adopted  for  hauling  the  raw  materials  and  the 
mixed  concrete.  It  is  worth  while  always  in  stock  piles  of 
any  size,  to  lay  a  flooring  of  plank  particularly  under  the  stone 
pile ;  if  dumped  directly  on  the  ground  it  costs  half  as  much 
again  to  handle  stone.  Current  practice  warrants  everything 
from  a  continuous  bank,  to  piles  from  1,000  to  1,500  ft.  apart, 
in  the  spacing  of  stock  piles. 

HINTS  ON  HAND  MIXING.— All  but  a  small  percentage 
of  the  concrete  annually  laid  in  street  work  is  hand  mixed. 
The  authors  are  confident  that  this  condition  will  disappear  as 
contractors  learn  more  of  the  advantages  of  machine  mixing,, 
but  it  prevails  at  present.  The  general  economics  of  hand 


290  CONCRETE    CONSTRUCTION. 

mixing  are  discussed  in  Chapter  II ;  in  street  work  as  before 
stated,  the  big  items  of  labor  cost  are  the  costs  of  handling 
materials  and  the  data  in  Chapter  II  on  these  processes  de- 
serve special  attention.  It  is  particularly  worth  noting  that  it 
is  seldom  economical  to  handle  materials  in  shovels  where 
carrying  is  necessary ;  it  is  a  common  thing  in  street  work  to 
see  an  attempt  to 'get  the  stock  piles  so  close  to  the  mixing 
board  that  the  material  can  be  handled  with  shovels,  and  this 
is  nearly  always  an  economic  error.  Street  work  is  readily 
measured ;  in  fact,  its  progress  can  be  seen  at  a  glance,  and 
advantage  cim  often  be  taken  of  this  fact  to  profit  by  the  ri- 
valry of  separate  gangs.  The  authors  have  known  of  the  labor 
costs  being  reduced  as  much  as  25  per  cent.,  due  to  pitting  one 
gang  against  another  where  each  could  see  the  progress  made 
by  the  other. 

METHODS  OF  MACHINE  MIXING.— Concrete  mixers 
have  been  slow  to  replace  handwork  in  laying  pavement  foun- 
dations. In  explanation  of  this  fact  it  is  asserted:  (i)  That 
frequent  shifting  of  the  mixer  causes  too  much  lost  time,  and 
(2)  that  the  principal  item  of  labor  cost  in  street  work  is  the 
conveying  of  materials  to  and  from  the  mixer,  and  this  item 
is  the  same  whether  hand  or  machine  mixing  be  employed. 
The  records  of  machine  mixer  work  given  elsewhere  in  this 
chapter  go  far,  in  the  opinion  of  the  authors,  toward  disprov- 
ing the  accuracy  of  both  assertions.  If  the  machine  used  and 
the  methods  of  work  employed  are  adapted  to  the  conditions 
of  street  work,  machine  mixing  can  be  employed  to  decided 
advantage. 

A  continuous  and  large  output  is  demanded  in  a  mixer  for 
street  work;  the  perfection  of  the  mixing  is  within  limits  a 
minor  consideration.  This  at  once  admits  for  consideration 
types  of  mixers  whose  product  is  classed  as  unsuitable  for 
reinforced  concrete  work,  and  also  admits  of  speeding  up  the 
output  of  the  better  types  to  a  point  beyond  that  at  which  they 
turn  out  their  most  perfect  product.  Keeping  these  facts  in 
mind  either  of  the  following  two  systems  of  work  may  be  em- 
ployed: (i)  Traction  plants  which  travel  with  the  work  and 
deposit  concrete  in  place,  or  so  nearly  in  place  that  little 
shoveling  is  necessary;  (2)  portable  plants  which  are  set  up 
at  wide  intervals  along  the  work  and  which  discharge  the 


PAVEMENT  FOUNDATION.  291 

concrete  into  carts  or  dump  wagons  which  distribute  it  to  the 
work. 

The  secret  of  economic  work  with  plants  of  the  ciass  cited 
first  is  the  distribution  of  the  stock  piles  so  as  practically  to 
eliminate  haulage  from  stock  pile  to  mixer.  The  mixer  backs 
away  from  the  work,  its  discharge  end  being  toward  the  work 
and  its  charging  end  away  from  it.  Then  deposit  the  mate- 
rials so  as  to  form  a  continuous  stock  pile  along  the  center  of 
the  street ;  the  mixer  moving  backward  from  the  completed 
foundation  keeps  close  to  the  materials  and  if  the  latter  are 
uniformly  distributed  in  the  pile  the  great  bulk  of  the  charging 
is  done  by  shoveling  direct  into  the  charging  bucket.  The 
point  to  be  watched  here  is  that  the  shovelers  d'o  not  have  to 
carry  the  materials ;  separate  stock  piles  within  moderate  haul- 
ing distance  by  wheelbarrows  are  a  far  more  economic  ar- 
rangement than  a  continuous  pile  so  irregularly  distributed 
that  much  of  the  material  has  to  be  carried  even  a  few  paces  in 
shovels. 

Economic  work  with  plants  of  the  second  class  depends 
upon  efficient  and  adequate  means  of  hauling  the  mixed  con- 
crete to  the  work.  The  plant  should  not  be  shifted  oftener 
than  once  in  1,000  to  2,000  ft.,  or,  say,  four  city  blocks.  This 
does  away  with  the  possibility  of  wheelbarrow  haulage ;  large 
capacity  hand  or  horse  carts  must  be  employed.  With  6  cu.  ft. 
hand  carts,  such  as  the  Ransome  cart,  a  haul  of  500  ft.  each 
way  from  the  mixer  is  possible  and  with  horse  carts,  such  as 
the  Briggs,  this  economic  distance  is  increased  to  1,000  ft.  each 
way  from  the  mixer.  The  mixer  must  be  close  to  the  stock 
pile  and  it  will  pay  to  make  use  of  improved  charging  devices. 
A  6-in.  foundation  for  2,000  ft.  of  3O-ft.  street  calls  for  667  cu. 
yds.  of  concrete,  and  if  both  sides  are  curbed  at  the  same  time, 
100  cu.  yds.  more  are  added,  or  767  cu.  yds.  in  all;  where  in- 
tersecting streets  are  to  be  paved  in  both  directions  from  the 
mixer  plant  these  amounts  are  doubled.  A  very  small  saving 
per  cubic  yard  due  to  mechanical  handling  of  the  materials  to 
the  mixer  amounts  to  the  interest  on  a  considerable  invest- 
ment in  such  plant.  A  point  that  should  not  be  forgotten  is 
that  carts  such  as  those  named  above  spread  the  concrete  in 
dumping  "so  that  little  or  no  shoveling  is  required. 


292 


CONCRETE    CONSTRUCTION. 


FOUNDATION  FOR  STONE  BLOCK  PAVEMENT, 
NEW  YORK,  N.  Y.— Mr.  G.  W.  Tillson,  in  "Street  Pave- 
ments and  Paving  Materials,"  p.  204,  gives  the  following  data 
on  the  cost  of  granite  block  pavement  in  New  York  City  in 
1899.  The  day  was  10  hours  long: 

Per  Per  Per 

Concrete  gang —  day.         sq.  yd.       cu.  yd. 

t  foreman    $  3.00       $0.0125       $0.075 

8  mixers  on  two  boards,  at  $1.25. . .  10.00  0.0416  0.250 
4  wheeling  stone  and  sand,  at  $1.25.  5.00  0.0208  0.125 
i  carrying  cement  and  supplying 

water,  at  $1.25 1.25         0.0051         0.031 

i   ramming,  at  $1.25 1.25         0.0051         0.031 

Total,  240  sq.  yds.  (40  cu.  yds.)  .$20.50      $0.0851       $0.512 
The  concrete  w'as  shoveled  direct  from  the  mixing  boards 
to  place. 

Cost  1-2-4  concrete —  Per  cu.  yd. 

iVs  bbls.  natural  cement,  at  $0.90 .$1.20 

0.95  cu.  yd.  stone,  at  $1.25 1.19 

0.37  cu.  yd.  sand,  at  $1.00 , 0.37 

Labor   0.51 


$3-27 

In  laying  5,167  sq.  yds.  of  granite  block  pavement  on  one 
job  in  New  York  City  in  1905,  the  authors'  records  show  th^t 
one  laborer  mixed  and  laid  1.3  cu.  yds.  of  concrete  per  day  in  a 
6-in.  foundation  ;  this  is  a  very  small  output.  The  work  was 
done  by  contract  and  the  labor  cost  was  as  follow  s : 

Per  Per 

Item.  Total.          sq.  yd.         cu.  yd. 

2&y2  days  foreman  at  $3.50 $  99.75         $0.0193        $0.118 

399  days  laborers  at  $1.75 698.25  0.1351  0.826 

$798.00         $0.1544         $0.944 

The  average  day's  wages  was  $1.86,  so  that  the  labor  cost 
was  about  0.5  'of  a  day's  wages  per  cubic  yard  of  concrete. 

FOUNDATION  FOR  PAVEMENT,  NEW  ORLEANS, 
LA. — Mr.  Alfred  E.  Harley  states  that  in  laying  concrete 
foundations  for  street  pavement  in  New  Orleans,  a  day's  work, 


PAVEMENT  FOUNDATION. 


293 


in  running  three  mixing  boards,  covering  the  full  width  of  the 
street,  averaged  900  sq.  yds.,  6  ins.  thick,  or  150  cu.  yds.,  with 
a  gang  of  40  men.  With  wages  assumed  to  be  15  cts.  per  hour 
the  labor  cost  was : 

Cts.  per 
cu.  yd. 

6  men  wheeling  broken  stone 6 

3  men  wheeling  sand 3 

1  man  wheeling  cement I 

2  men  opening  cement 2 

7  men   dry  mixing , 7 

8  men  taking  concrete  off 8 

3  men  tamping 3 

3  men  grading  concrete 3 

1  man  attending  run  planks I 

3  water  boys I 

2  extra  men  and  i  foreman 4 


Total  labor  cost .   39  cts. 

FOUNDATIONS  FOR  STREET  PAVEMENT,  TO- 
RONTO, CANADA.— The  following  cost  of  a  concrete  base 
for  pavements  at  Toronto  has  been  abstracted  from  a  report 
(1892)  of  the  City  Engineer,  Mr.  Granville  C.  Cunningham. 
The  concrete  was  1-2^-7^2  Portland ;  2,430  eu.  yds.  were  laid, 
the  thickness  being  6  ins.,  at  the  following  cost  per  cubic  yard: 

0.77  bbl.  cement,  at  $2.78 $2.14 

0.76  cu.  yd.  stone,  at  $1.91 1.45 

0.27  cu.  yd.  sand  and  gravel,  at  $0.80 0.22 

Labor  (15  cts.  per  hr.) 1.03 


Total $4.84 

Judging  by  the  low  percentage  cf  stcne  in  so  lean  a  mixture 
as  the  above,  the  concrete  was  not  fully  6  ins.  thick  as  as- 
sumed by  Mr.  Cunningham.  Note  that  the  labor  cost  was  1^2 
to  2  times  what  it  would  have  been  under  a  good  contractor. 

MISCELLANEOUS  EXAMPLES  OF  PAVEMENT 
FOUNDATION  WORK.— The  following  records  of  pave- 
ment foundation  work  are  taken  from  the  note  and  time  books 
of  one  of  the  authors : 

Case  I. — Laying  6-in.  pavement  foundation;  stone  delivered 
and  dumped  upon  2-in.  plank  laid  to  receive  it.  Sand  and 


294  CONCRETE    CONSTRUCTION. 

stone  were  dumped  along  the  street,  so  that  the  haul  in  wheel- 
barrows to  mixing  board  was  about  40  ft.  Two  gangs  of  men 
worked  under  separate  foremen,  and  each  gang  averaged  4.5 
cu.  yds.  concrete  per  hour.  The  labor  cost  was  as  follows  for 
45  cu.  yds.  per  gang: 

Per  Per 

day.        cu.  yd, 

4  men  filling  barrows  with  stone  and  sand 
ready   for    the    mixers,    wages    15    cts. 

per  hour $6.00  $0.13 

10  men,  wheeling,   mixing  and   shoveling  to 
place  (3  or  4  steps),  wages  15  cts.  per 

hour   ._ 15.00  0.33 

2  men  ramming,  wages  15  cts.  per  hour.~..  .     3.00  0.07 

I  foreman  at  30  cts.  per  hour  and   I   water 

boy,  5  cts 3.50  0.08 

Total $27.50  $0.61 

Case  II. — Sometimes  it  is  desirable  to  know  every  minute 
detail  cost,  for  which  purpose  the  following  is  given : 

Per  cu.  yd. 

Day's  labor.  Cost. 

3  men  loading  stones  into  barrows $0.06  $0.09 

1  man  loading  sand  into  barrows 0.02  0.03 

2  men  ramming 0.04  0.06 

i  foreman  and  I  water  boy  equivalent  to.  ...   0.035  0.05 

Wheeling  sand  and  cement  to  mixing  board.  .   0.02  0.03 

Wheeling  stone  to  mixing  board. 0.026  0.04 

9  men  mixing  mortar 0.013  0.02 

Mixing  stone  and  mortar 0.049  0.07 

Placing  concrete  (walking  15  ft.) 0.072  o.n 

Total    $0.335  $0-50 

In  one  respect  this  is  not  a  perfectly  fair  example  (although 
it  represents  ordinary  practice),  for  the  mortar  was  only 
turned  over  once  in  mixing  instead  of  three  times,  and  the 
stone  was  turned  only  twice  instead  of  three  or  four  times. 
Water  was  used  in  great  abundance,  and  by  its  puddling  ac- 
tion probably  secured  a  very  fair  mixture  of  cement  and  sand, 
and  in  that  way  secured  a  better  mixture  than  would  be  ex- 


PAVEMENT  FOUNDATION.  295 

pected  from  the  small  amount  of  labor  expended  in  actual 
mixing.  About  9  cts.  more  per  cu.  yd.  spent  in  mixing  would 
have  secured  a  perfect  concrete  without  trusting  to  the  water. 
Case  III. — Two  gangs  (34  men)  working  under  separate 
foremen  averaged  600  sq.  yds.,  or  100  cu.  yds.  of  concrete  per 
lo-hour  day  for  a  season.  This  is  equivalent  to  3  cu.  yds.  per 
man  per  day.  The  stone  and  sand  were  wheeled  to  the  mixing 
board  in  barrows,  mixed  and  shoveled  to  place.  Each  gang 
was  organized  as  follows: 

Per  Per 

day.  cu.  yd. 

4  men   loading  barrows $  6.00  $0.12 

9  men  mixing  and  placing I3-5O  0.27 

2  men  tamping 3.00  0.06 

i   foreman    2.50  0.05 


.Total    $25.00  $0.50 

These  men  worked  with  great  rapidity.  The  above  cost  of 
50  cts.  per  cu.  yd,  is  about  as  low  as  any  contractor  can  rea- 
sonably expect  to  mix  and  place  concrete  by  hand  in  pave- 
ment work. 

Case  IV. — Two  gangs  of  men,  34  in  all,  working  side  by  side 
on  separate  mixing  boards,  averaged  720  sq.  yds.,  or  120  cu. 
yds.,  per  lo-hour  day.  Each  gang  was  organized  as  follows : 

Per  Per 

day.  cu.  yd. 

6  men  loading  and  wheeling $  9.00  $0.15 

8  men  mixing  and  placing 12.00  0.20 

2  men  tamping   3.00  0.05 

I  foreman    3.00  0.05 


Total $27.00  $0.45 

Instead  of  shoveling  the  concrete  from  the  mixing  board 
into  place,  the  mixers  loaded  it  into  barrows  and  wheeled  it  to 
place.  The  men  worked  with  great  rapidity. 

Mr.  Irving  E.  Howe  gives  the  cost  of  a  6-in.  foundation  of 
1-3-5  natural  cement  at  Minneapolis,  Minn.,  in  1897,  as  $2.80 
per  cu.  yd.,  or  $0.467  per  sq.  yd.  Cement  cost  76  cts.  per 
barrel  and  stone  and  sand  cost  delivered  $1.15  and  30  cts. 
respectively.  Mixers  received  $1.75  per  day. 


296  CONCRETE    CONSTRUCTION. 

Mr.  Niles  Meriwether  gives  the  cost  of  materials  and  labor 
for  an  8-in.  foundation  constructed  by  day  labor  (probably 
colored)  at  Memphis,  Term.,  in  1893,  as  follows: 

Per  sq.  yd. 

Natural  cement  at  $0.74  per  bbl $0.195 

Sand  at  $1.25  per  cu.  yd 0.075 

Stone  at  $1.87  per  cu.  yd 0.355 

Labor  mixing  and  placing 0.155 


Total   $0.780 

Labor  was  paid  $1.25  to  $1.50  per  8-hour  day  and  1.16  bbls. 
of  cement  were  used  per  cubic  yard  of  concrete.  The  cost  of 
materials,  as  will  be  noted,  was  high  and  the  labor  seems  to 
have  been  inefficient. 

FOUNDATIONS  FOR  BRICK  PAVEMENT,  CHAM- 
PAIGN, ILL. — The  concrete  foundation  for  a  brick  pavement 
constructed  in  1903  was  6  ins.  thick;  the  concrete  used  was 
composed  of  I  part  natural  cement,  3  parts  of  sand  and  gravel, 
and  3  parts  of  broken  stone.  All  the  materials  were  mixed 
with  shovels,  and  were  thrown  into  place  from  the  board  upon 
which  the  mixing  was  done.  The  material  was  brought  to  the 
steel  mixing  board  in  wheelbarrows  from  piles  where  it.  had 
been  placed  in  the  middle  of  the  street,  the  length  of  haul 
being  usually  from  30  to  60  ft.  The  foundation  was  6  ins. 
thick  and  it  cost  as  follows  for  materials  and  labor : 

Cost  per 
cu.  yd. 

1.2  bbls.  cement,  at  $0.50 $0.600 

O.6  cu.  yd.  sand  and  gravel,  at  $i 0.600 

0.6  cu.  yd.  broken  stone,  at  $1.40 0.840 

6  men  turning  with  shovels,  at  $2 0.080 

4  men  throwing  into  place,  at  $2 O-°53 

2  men  handling  cement,  at  $1.75 0.023 

1  man  wetting  with  hose,  at  $1.75.  .  .  * 0.012 

2  men  tamping,  at  $1.75 0.023 

I  man  leveling,  at  $1.75 0.012 

6  men  wheeling  stone,  at  $1.75 0.070 

4  men  wheeling  gravel,  at  $1.75 0.047 

I  foreman,  at  $4 » 0.027 

$2.387 


PAVEMENT  FOUNDATION. 


297 


This  is  practically  40  cts.  per  sq.  yd.,  or  $2.40  per  cu.  yd.  of 
concrete  for  materials  and  labor.  It  is  evident  from  the  above 
quantities  t'hat  a  cement  barrel  was  assumed  to  hold  about  4.5 
cu.  ft.,  hence  the  cement  was  measured  loose  in  making  the 
1-3-3  concrete.  The  accuracy  of  the  quantities  given  is  open 
to  serious  doubt.  It  will  also  be  noted  that  the  labor  cost  of 
making  and  placing  the  concrete  was  only  35  cts.  per  cu.  yd., 
wages  being  nearly  $1.85  per  day.  This  is  so  remarkably  low 
that  some  mistake  would  seem  to  have  been  made  in  the  meas- 
urement of  the  work.  The  authors  do  not  hesitate  to  say  that 
no  gang  of  men  ever  made  any  considerable  amount  of  con- 
crete by  hand  at  the  rate  of  5.75  cu.  yds.  per  man  per  day. 


Fig.  112. — Foote  Continuous  Mixer  Arranged  for  Pavement  Foundation  Work. 

FOUNDATION  CONSTRUCTION  USING  CONTIN- 
UOUS MIXERS.— The  following  are  records  of  two  jobs  of 
pavement  foundation  work  using  continuous  mixers  with  one- 
horse  concrete  carts  in  one  instance  and  wheelbarrows  in  the 
other  instance.  The  mixer  used  was  the  Foote  mixer,  as  ar- 
ranged for  the  work  being  described  it  is  shown  by  Fig.  112. 
One  particular  advantage  of  this  and  similar  mixers  for  street 
work  is  that  no  proportioning  or  measuring  of  the  materials 
is  required  of  the  men.  The  mixers  are  provided  with  an 
automatic  measuring  device,  by  means  of  which  any  de- 
sired proportion  of  cement,  sand  and  stone  is  delivered  to 
the  mixing  trough.  The  mixer  is  mounted  on  trucks,  and 


298 


CONCRETE    CONSTRUCTION. 


the  hoppers  that  receive  the  sand  and  stone  are  comparatively 
low  down.  The  sand  can  be  wheeled  in  barrows  up  a  run  plank 
and  dumped  into  a  hopper  on  one  side  of  the  mixer,  and  in 
like  manner  the  gravel  tor  broken  stone  can  be  delivered  into  a 
hopper  on  the  other  side.  The  cement  is  delivered  in  bags  or 
buckets  to  a  man  who  dumps  it  into  a  cement  hopper  directly 
over  the  mixer.  All  that  the  operator  needs  to  attend  to  is  to 
see  that  the  men  keep  the  hoppers  comparatively  full.  The 
records  of  work  on  the  two  jobs  mentioned  are  as  follows : 

Job  I. — The  sand  was  delivered    from   the    stock   pile   by   a 
team  hitched  to  a  drag  scraoer,  and  was  dumped  alongside 


Fig:      113. — Briggs    Cart    Distributing    Concrete    for    Pavement    Foundation. 

the  mixer  where  two  men  shoveled  it  into  the  hopper.  On 
the  same  job  the  concrete  was  hauled  away  from  the  mixer  in 
Briggs'  concrete  .carts.  With  a  gang  of  30  men  and  2  to  4 
horses  hauling  concrete  in  Briggs'  carts,  the  contractor  aver- 
aged 1,200  sq.  yds.,  or  200  cu.  yds.,  per  day  of  10  hours.  With 
wages  of  laborers  at  15  cts.  per  hour,  and  a  single  horse  at  the 
same  rate,  the  cost  of  labor  was  26  cts.  per  cu.  yd.,  or  less  than 
4l/2  cts.  per  sq.  yd.  of  concrete  base  6  ins.  thick.  The  coal  was 
a  nominal  item,  and  did  not  add  i  ct.  per  cu.  yd.  to  the  cost. 


PAVEMENT  FOUNDATION.  299 

In  this  case  the  mixer  was  set  up  on  a  side  street  and  the 
concrete  was  hauled  in  the  carts  for  a  distance  of  a  block  each 
way  from  the  mixer.  At  first  four  carts  were  used,  but  as  the 
concreting  approached  the  mixer,  less  hauling  was  required, 
and  finally  only  two  carts  were  used.  An  illustration  of  a 
Briggs  cart  is  given  by  Fig.  113;  it  is  hauled  by  one  horse, 
which  the  driver  leads,  and  is  dumped  by  an  ingenious  device 
operated  from  the  horse's  head.  The  cart  dumps  from  the 
bottom  and  spreads  the  load  in  a  layer  about  8  or  9  ins.  thick, 
so  that  no  greater  amount  of  shoveling  is  necessary  than  when 
barrows  are  used.  It  took  about  20  seconds  for  the  cart  to 
back  up  and  get  its  load  and  about  5  seconds  to  dump  and 
spread  the  load. 

Job  II. — In  this  job  the  mixer  was  charged  with  wheel- 
barrows and  wheelbarrows  were  also  employed  to  take  the 
mixed  concrete  to  the  work,  the  mixer  being  moved  forward 
at  frequent  intervals.  The  stock  piles  were  continuous,  sand 
on  one  side  of  the  street  and  stone  on  the  other  side.  A  1-3-6 
Portland  cement  concrete  was  used,  a  very  rich  mixture  for  a 
6-in.  foundation.  The  organization  of  the  working  gang  was 
as  follows : 

Men  loading  and  wheeling  gravel 8 

Men  assisting  in  loading  gravel 2 

Man  dumping  barrows  into  hopper i 

Men  loading  and  wheeling  sand 3 

Man  dumping  barrows  into  hopper i 

Men  wheeling  concrete  in  barrows 7 

Men  spreading  concrete 3 

Men  tamping   concrete 2 

Man  pouring  cement  into  hopper i 

Man  operating  mixer    i 

Man  shoveling  spilled  concrete i 

Man  opening  cement  bags i 

Engineer    i 

Total  men  in  gang 32 

The  average  day's  output  of  this  gang  was  150  cu.  yds.,  or 
900  sq.  yds.  in  8  hours ;  but  on  the  best  day's  work  the  output 
was  200  cu.  yds.,  or  1,200  sq.  yds.  in  8  hours,  which  is  a  re- 
markable record  for  32  men  and  a  mixer  working  only  8  hours. 


300  CONCRETE    CONSTRUCTION. 

The  following  is  the  labor  cost  of  8,896  sq.  yds.  !of  4^-in. 
concrete  foundation  for  an  asphalt  pavement  constructed  in 
New  York  City  in  1904: 

Item.  Per  sq  yd. 

Foreman  at  $3.75 $0.030 

Laborers  at  $1.50 0.242 

Teams  at  $5 0.040 

Steam  engine  at  $3.50 0.028 


Total   ........................................  $0.340 

The  concrete  was  a  1-3-6  mixture  and  was  mixed  in  a  Foote 
mixer.  These  costs  are  compiled  from  data  collected  by  tlie 
authors. 

FOUNDATION  CONSTRUCTION  FOR  STREET 
RAILWAY  TRACK  USING  CONTINUOUS  MIXERS.- 

The  following  account  of  the  methods  and  cost  of  construct- 
ing a  concrete  foundation  for  street  railway  track  at  St.  Louis, 


/|  'Refined  Asphalt^      ^  ,  in  H/l^  "Bituminous  Binder 

'-  —  •  —- 


XV^xV^-^-i^^ 


Fig.    114.— Concrete    Foundation    for    Street    Railway    Track. 

Mo.,  is  compiled  from  information  published  by  Mr.  Richard 
McCulloch.  The  work  was  done  by  day  labor  by  the  United 
Railways  Co.,  in,  1906.  Figure  114  shows  the  concrete  con- 
struction. A  i-2y2-6l/2  Portland  cement,  broken  stone  con- 
crete mixed  by  machine  was  used. 

The  material  for  the  concrete  was  distributed  on  the  street 
beside  the  tracks  in  advance  of  the  machine,  the  sand  being 
first  deposited,  then  the  crushed  rock  piled  on  that,  and  finally 
the  cement  sacks  emptied  on  top  of  this  pile.  The  materials 
were  shoveled  from  this  pile  into  the  concrete  mixing  machine 
without  any  attempt  at  hand  mixing  on  the  street.  Great  care 
was  taken  in  the  delivery  of  materials  on  the  street  to  have 
exactly  the  proper  quantity  of  sand,  rock  and  cement,  so  that 
there  would  be  enough  for  the  ballasting  of  the  track  to  the 


PAVEMENT  FOUNDATION.  301 

proper  height  and  that  none  would  be  left  over.  Each  car  was 
marked  with  its  capacity  in  cubic  feet,  and  each  receiver  was 
furnished  with  a  table  by  which  he  could  easily  estimate  the 
number  of  lineal  feet  of  track  over  which  the  load  should  be 
distributed. 

The  concrete  mixing  machines  were  designed  and  built  in 
the  shops  of  the  United  Railways  Co.  Three  machines  were 
used  in  this  work,  one  for  each  gang.  The  machine  is  com- 
posed of  a  Drake  continuous  worm  mixer,  fed  by  a  chain 
dragging  in  a  cast-iron  trough.  The  trough  is  36  ft.  long,  so 
that  there  is  room  for  14  men  to  shovel  into  it.  Water  is 
sprayed  into  the  worm  after  the  materials  are  mixed  dry.  This 
water  was  obtained  from  the  fire  plugs  along  the  route.  In 
the  first  machine  built,  the  Drake  mixer  wras  8  ft.  long.  In 
the  two  newer  machines  the  mixer  was  10  ft.  long.  Both  the 
conveyor  and  the  mixer  were  motor  driven,  current  being  ob- 
tained for  this  purpose  from  the  trolley  wire  overhead.  Two 
types  of  machines  were  used,  one  in  which  the  conveyor 
trough  was  straight  and  45  in.  above  the  rail,  and  the  other  in 
which  the  conveyor  trough  was  lowered  back  of  the  mixer, 
being  25  in.  above  the  rail.  The  latter  type  had  the  advantage 
of  not  requiring  such  a  lift  in  shoveling,  but  the  trough  is  so 
low  that  a  motor  truck  cannot  be  placed  underneath  it.  In  the 
high  machine  the  mixer  is  moved  forward  by  a  standard  motor 
truck  under  the  conveyor.  In  the  low  machine  the  mixer  is 
moved  by  a  ratchet  and  gear  on  the  truck  underneath  the 
mixer.  A  crew  of  27  men  is  required  to  work  each  machine, 
and  under  average  conditions  concrete  for  80  lin.  ft.  of  single 
track,  amounting  to  22  cu.  yds.,  can  be  discharged  per  hour. 

The  costs  of  the  concrete  materials  delivered  per  cubic  yard 
of  concrete  were:  Cement,  per  barrel,  $1.70;  sand,  per  cu.  yd., 
$0.675,  anci  stone,  per  cu.  yd.,  $0.425.  The  cost  of  the  concrete 
work  per  cubic  yard  and  per  lineal  foot  of  track  was  as 
follows : 

Item.  Per  lin.  ft.  Per  cu.  yd. 

Concrete  materials   $0.791  $2.92 

Labor  mixing  and  placing 0.071  0.26 

Total  labor  and  materials...     $0.862  $3.18 


302  CONCRETE    CONSTRUCTION. 

FOUNDATION  CONSTRUCTION  USING  BATCH 
MIXERS  AND  WAGON  HAULAGE,  ST.  LOUIS,  MO.— 

The  following  record  of  the  method  and  cost  of  laying  a  con- 
crete foundation  for  street  pavement  using  machine  mixing 
and  wagon  haulage  is  given  by  Mr.  D.  A.  Fisher.  The  founda- 
tion was  6  ins.  thick.  The  gravel  was  dumped  from  wagons 
into  a  large  hopper,  raised  by  a  bucket  elevator  into  bins,  and 
drawn  off  through  gates  into  receiving  hoppers  on  the  charg- 
ing platform  where  the  cement  was  added.  The  receiving 
hoppers  discharged  into  the  mixers,  which  discharged  the 
mixed  concrete  into  a  loading  car  that  dumped  into  wagons, 
which  delivered  it  on  the  street  where  wanted.  The  longest 
haul  in  wagons  was  30  mins.,  but  careful  tests  showed  that  the 
concrete  had  hardened  well.  The  wagons  were  patent  dump 
wagons  of  the  drop-bottom  type.  Mr.  Fisher  says : 

"You  may  consider  the  following  figures  a  fair  average  of 
the  plant  referred  to,  working  to  its  capacity.  To  these 
amounts,  however,  must  be  added  the  interest  on  the  invest- 
ment, the  cost  of  wrecking  the  plant  and  the  depreciation  of 
the  same,  superintendence,  and  the  pay  roll  that  must  be 
maintained  in  wet  weather.  I  am  assuming  the  street  as 
already  brought  to  grade  and  rolled. 

"With  labor  at  $1.75  per  day  of  10  hours,  teams  at  $4,  en- 
gineer and  foremen  at  $3,  and  engine  at  $5  per  day,  concrete 
mixed  and  put  in  place  by  the  above  method  costs : 

Per  cu.  yd. 

To  mix    $0.12  to  $0.15 

To  deliver  to  street o.io  to    0.14 

To  spread  and  tamp  in  place 0.08  to    o.i  i 


Total    $0.30  to  $0.40 

"The  mixers  are  No.  2l/2  Smith,  sold  by  the  Contractors' 
Supply  Co,,  Chicago,  111.,  and  a  l/2  yd.  cube,  sold'  by  Municipal 
Engineering  &  Contracting  Co.,  Chicago. 

"The  above  figures  are  on  the  basis  of  a  batch  every  2  min- 
utes, which  is  easily  maintained  by  using  the  loading  car,  as 
by  this  means  there  will  be  no  delay  in  the  operation  of  the 
plant  owing  to  the  irregularity  of  the  arrival  of  the  teams. 

"My  experience  leads  me  to  believe  that  a  better  efficiency 
can  be  obtained  by  using  mixers  of  i  cu.  yd.  capacity,  and  that 


PAVEMENT  FOUNDATION. 


303 


the  batch  mixer  is  the  only  type  of  machine  where  any  cer- 
tainty of  the  proportion  of  the  mixture  is  realized." 

FOUNDATION  CONSTRUCTION  USING  A  TRAC- 
TION MIXER. — In  laying  a  6-in.  foundation  for  an  asphalt 
pavement  in  Buffalo,  N.  Y.,  an  average  of  100  sq.  yds.,  or  16.6 
cu.  yds.,  of  concrete  in  place  was  made  per  hour  using  the 
traction  mixer  shown  by  Fig.  115.  This  mixer  was  made  by 
the  Municipal  Engineering  &  Contracting  Co.,  of  Chicago, 
111.,  and  consisted  of  one  of  that  company's  improved  cube 
mixers  operated  by  a  gasoline  engine  and  equipped  with  the 
regulation  mechanical  charging  device  and  also  with  a  swing- 
ing conveyor  to  deliver  the  mixed  concrete  to  the  work.  The 
featur^  of  the  apparatus  in  its  application  to  paving  work  is 
the  conveyor.  This  was  25  ft.  long  and  pivoted  at  the  mixer 
end  so  as  to  swing  through  an  arc  of  170°.  The  mixer  dis- 
charged into  a  skip  or  bucket  traveling  on  the  conveyor  frame 


Fig.  115. — Chicago  Improved  Cube  Traction  Mixer  for  Pavement  Foundation. 

and  discharging  over  the  end  spreading  its  load  anywhere 
within  a  radius  of  25  ft.  In  operation  the  mixer  traveled  along 
the  center  of  the  street,  backing  away  from  the  finished 
foundation  and  toward  the  stock  pile,  which  was  continuous 
and  was  deposited  along  the  center  of  the  street.  The  bulk  of 
the  sand  and  stone  was  thus  shoveled  direct  into  the  charging 
bucket  and  the  remainder  was  wheeled  to  the  bucket  in  bar- 
rows. As  the  charging  bucket  is  only  14  ins.  high  the  bar- 
rows could  be  dumped  directly  into  it  from  the  ground.  The 
gang  worked  was  17  including  a  foreman  and  one  boy,  and 


304  CONCRETE    CONSTRUCTION. 

with  this  gang  100  sq.  yds.  of  6-in.  foundation  was  laid  per 
hour.  Assuming  an  average  wage  of  20  cts.  an  hour  the  cost 
of  mixing  and  placing  the  foundation  concrete  was  3.4  cts.  per 
sq.  yd.  or  20.4  cts.  per  cu.  yd.  for  labor  alone. 

FOUNDATION  CONSTRUCTION  USING  CONTINU- 
OUS MIXER. — The  foundation  was  6  ins.  thick  for  an  asphalt 
pavement  and  was  laid  in  Chicago,  111.  The  concrete  used  was 
exceptionally  rich  for  pavement  foundation  work,  it  being  a 
1-3-6  Lehigh  Portland  Cement,  broken  stone  mixture.  The 
mixing  was  done  by  machine,  a  mixer  made  by  the  Buffalo 
Concrete  Mixer  Co.,  Buffalo,  N.  Y.,  being  used.  This  mixer 
was  equipped  with  an  elevating  charging  hopper  and  was 
operated  as  a  continuous  mixer.  The  mixer  was  mounted 
on  wheels  and  was  pulled  along  the  center  of  the  street  ahead 
of  the  work  with  its  discharge  end  toward  the  work.  Moves 
of  about  25  to  30  ft.  were  made,  the  mixer  being  pulled  ahead 
for  this  distance  each  time  that  the  concrete  came  up  to  its 
discharge  end.  The  stock  piles  were  continuous,  sand  on  one 
side  and  stone  on  the  other  side  of  the  street.  Cement  was 
stored  in  a  pile  at  each  end  of  the  block.  All  materials  were 
wheeled  from  stock  piles  to  mixer  in  wheelbarrows.  The 
men  wheeling  sand  and  stone  loaded  their  own  barrows, 
wheeled  them  to  the  mixer  and  discharged  them  directly  into 
the  elevating  hopper.  No  runways  were  used,  the  barrows 
being  wheeled  directly  on  the  ground.  The  cement  was 
brought  in  barrows,  two  or  three  bags  being  a  load,  and 
dumped  alongside  a  cement  box  which  was  located  close  to 
and  at  one  side  of  the  elevating  hopper.  A  man  untied  the 
bags  and  emptied  them  into  the  cement  box  and  another  man 
scooped  the  cement  out  of  the  box  in  bucketfuls  and  emptied 
it  over  the  sand  and  stone  in  the  elevating  hopper.  The  mixer 
discharged  onto  a  sheet  iron  shoveling  board,  and  the  concrete 
was  carried  in  shovels  from  shoveling  board  to  place,  the 
length  of  carry  being  a  maximum  of  25  to  30  ft.  Two  men 
were  required  to  pull  down  the  cone  of  concret.e  at  the  dis- 
charge end  of  the  mixer  and  to  keep  the  stone  from  separating 
and  rolling  down  the  sides.  The  gang  was  organized  as 
follows : 


PAVEMENT  FOUNDATION.  305 

No.  Men, 

Loading  and  wheeling  stone . . . .^, .... .....  10 

Loading  and  wheeling  sand 3  to  4 

Loading  and  wheeling  cement 2 

Untieing  and  emptying  cement  bags. I 

Charging  cement  to  hopper I 

Operating  mixer  and  hopper I 

Pulling  down   and  tending  discharge 2 

Carrying  concrete  in  shovels , .  . .  .   8 

Spreading  concrete 2 

Tamping  concrete 2 

Sweeping    concrete    I 

General  laborers   3 

Foreman I 

Watchman    I 

Timekeeper I 

Total  gang 40 

This  gang'  averaged  1,000  sq.  yds.  of  6-in.  foundation  per 
lo-hour  day;  a  maximum  of  1,400  sq.  yds.  was  laid  in  a  day. 
We  have  thus  an  average  of  167  cu.  yds.  and  a  maximum  of 
234  cu.  yds.  of  concrete  foundation  mixed  and  placed  per 
lo-hour  day.  At  an  average  wage  of  $2  per  day  the  average 
labor  cost  of  mixing  and  placing  concrete  was  48  cts.  per  cu. 
yd.  or  8  cts.  per  sq.  yd.  of  6-in.  foundation.  It  was  stated  that 
the  gang  was  larger  by  three  men  than  was  ordinarily  used 
owing  to  certain  extra  work  being  done  at  the  time  that  the 
above  figures  were  collected.  Taking  out  three  extra  men  and 
the  timekeeper  and  watchman  we  get  34  men  actually  working 
in  mixing  and  placing  concrete.  This  reduced  gang  gives  us  a 
labor  cost  for  mixing  and  placing  of  about  41  cts.  per  cu.  yd. 
or  6.8  cts.  per  sq.  yd.  of  6-in.  foundation. 

FOUNDATION  CONSTRUCTION  USING  A  BATCH 
MIXER. — The  following  figures  are  an  average  of  several 
jobs  using  a  Ransome  V2-cu.  yd.  mixer  for  constructing  6-in. 
foundations.  The  mixer  was  moved  1,000  ft.  at  a  time  and  the 
work  conducted  500  ft.  in  each  direction  from  each  station. 
The  concrete  materials  were  delivered  from  stock  pile  to 
mixer  in  wheelbarrows  and  the  mixed  concrete  was  hauled  to 
the  work  in  two-wheeled  Ransome  carts.  Run  planks  were  laid 


306  CONCRETE    CONSTRUCTION. 

for  the  carts  and  one  man  readily  pushed  a  cart  holding  6  cu. 
ft.     The  men  had  to  work  fast  on  the  long  haul  but  had  an 
easy  time  when  the  haul  was  short.     The  organization  of  the 
gang  was  as  follows,  wages  being  $1.50  per  day: 
10  men  loading  and  wheeling  stone $I5-OO 

4  men  loading  and  wheeling  sand 6.00 

2  men  handling  cement 3.00 

I  fireman 2.00 

T   man  dumping  mixer 1.50 

5  men  wheeling  carts    7.50 

3  men  spreading  and  ramming 4-5O 

i  foreman    3.50 

Total  wages  per  day $43.00 

This  gang  averaged  1,080  sq.  yds.  of  6-in.  foundation  or  180 
cu.  yds.  of  concrete  in  place  per  day  which  gives  a  labor  cost 
of  24  cts  per  cu.  yd.  or  4  cts.  per  sq.  yd.  for  mixing  and 
placing. 


CHAPTER    XV. 

METHODS    AND    COST    OF    CONSTRUCTING    SIDE- 
WALKS, PAVEMENTS  AND  CURB  AND  GUTTER. 

Next  to  pavement  foundations  the  most  extensive  use  of 
concrete  in  street  work  is  for  cement  walks  and  concrete  curb 
and  gutter.  Usually  the  mixing  and  placing  of  the  concrete 
is  hand  work,  practically  the  only  exceptions  being  where 
pavement  base,  curbing  and  sidewalks  are  built  all  at  once, 
using  machine  mixers.  The  same  objections  that  have  been 
raised  to  machine  mixers  in  laying  pavement  foundation  are 
raised  against  them  for  curb  and  walk  construction,  and  owing 
to  the  much  smaller  yardage  per  lineal  foot  of  street  in  walk 
and  curb  work  these  objections  carry  more  force  than  they  do 
in  case  of  paving  work.  Another  argument  against  the  use  of 
mixers  is  that  both  walk  and  curb  and  gutter  work  involve  the 
use  of  forms  and  the  application  of  mortar  finish,  the  placing 
of  which  are  really  the  limiting  factors  in  the  rate  of  progress 
permissible,  and  this  rate  is  too  slow  to  consume  an  output 
necessary  to  make  a  mixer  plant  economical  as  compared  with 
hand  mixing  where  so  much  transportation  is  involved.  Con- 
crete sidewalk  and  curb  work  are  essentially  hand  mixing 
work;  they,  therefore,  involve  &  careful  study  of  the  econ- 
omies of  hand  mixing  and  wheelbarrow  haulage  which  are 
fully  discussed  in  Chapter  II. 

CEMENT    SIDEWALKS. 

Sidewalk  construction  consists  in  molding  on  a  suitably 
prepared  sub-base  a  concrete  slab  from  3^2  to  7^/2  ins.  thick, 
depending  on  practice,  and  finishing  its  top  surface  with  a 
y2  to  il/2-m.  wearing  surface  of  cement  mortar. 

GENERAL  METHOD  OF  CONSTRUCTION.— The  ex- 
cavation and  preparation  of  the  subgrade  call  for  little  notice 
beyond  the  warning  that  they  should  never  be  neglected.  The 
authors  have  seen  many  thousands  of  feet  of  cement  walk  laid 
in  the  middle  West  in  which  the  sub-base  was  placed  directly 

307 


308  CONCRETE    CONSTRUCTION. 

on  the  natural  sod,  often  covered  with  grass  and  weeds  a  foot 
high.  Such  practice  is  wholly  vicious.  The  sod  should 
always  be  removed  and  the  surface  soil  excavated  to  a  depth 
depending  upon  the  climate  and  nature  of  the  ground  and  the 
foundation  bed  well  tamped.  From  4  to  6  ins.  depth  of  exca- 
vation will  serve  where  the  soil  is  reasonably  hard  and  there 
are  no  heavy  frosts;  with  opposite  conditions  a  12-in.  exca- 
vation is  none  too  deep.  The  thickness  of  the  broken  stone, 
gravel,  cinder  or  sand  sub-base  should  likewise  be  varied  with 
the  character  of  the  soil,  the  conditions  of  natural  drainage 
and  the  prevalence  of  frost.  In  well  drained  sandy  soils  6  to 
8  ins.  of  sub-base  are  sufficient,  but  in  clayey  soils  with  poor 
natural  drainage  the  sub-base  should  be  from  10  to  12  ins. 
thick  at  least;  the  local  conditions  will  determine  the  thick- 
ness of  sub-base  necessary  and  in  places  it  may  be  desirable 
to  provide  by  artificial  drainage  against  the  accumulation  of 
water  under  the  concrete.  Tile  drains  are  better  and  cheaper 
than  excessively  deep  foundations.  The  thorough  tamping  of 
the  sub-base  is  essential  to  avoid  settling  and  subsequent 
cracking  of  the  concrete  slab.  This  is  a  part  of  sidewalk  work 
which  is  often  neglected. 

Portland  cement  concrete,  sand  and  broken  stone  or  gravel 
mixtures  in  the  proportions  of  1-3-5  and  1-3-6  are  used  for  base 
slabs.  For  walks  up  to  7  ft.  wide  the  slab  is  made  3^  ins. 
thick  for  residence  streets  and  4^  to  5  ins.  thick  for  business 
streets ;  for  wider  walks  the  thickness  is  increased  to  7  ins. 
for  8-ft.  width  and  7^2  ins.  for  9  to  lo-ft.  width.  Roughly 
the  thickness  of  the  walk  in  inches  (base  and  top  together)  is 
made  about  equal  to  its  width  in  feet.  The  concrete  is  de- 
deposited  in  a  single  layer  and  tamped  thoroughly,  either  in 
separate  blocks  behind  suitable  forms  or  in  a  continuous  slab 
which  is  while  fresh  cut  through  to  make  separate  blocks. 
For  walks  up  to  8  ft.  wide  the  slab  is  divided  by  transverse 
joints  spaced  about  the  width  of  the  walk  apart,  but  for  the 
wider  walks  the  safety  of  this  division  depends  upon  the  thick- 
ness of  the  base ;  an  8-ft.  walk  with  a  5-in.  base  can  safely  be 
laid  with  joints  8  ft.  apart,  but  if  the  slab  is  only  4  ins.  thick 
it  had  better  be  laid  in  4x4-ft.  squares.  The  mode  of  pro- 
cedure in  base  construction  is  as  follows: 


SIDEWALKS    AND    CURBS. 


309 


The  sub-base  being  laid,  side  forms  held  by  stakes  are 
placed  as  shown  by  Fig.  116,  with  the  top  edges  of  the  boards 
exactly  to  the  grade  of  the  top  surface  of  the  finished  walk. 
The  concrete  is  then  deposited  between  these  side  forms  and 
tamped  until  it  is  brought  up  to  the  level  marked  by  the 
templet  A.  If  the  plan  is  to  deposit  the  base  in  sections  trans- 
verse plates  of  y%  to  J4  m-  steel  are  set  across  the  walk  be- 


Fig.    116.— Sketch    Showing   Method  of   Constructing   Cement    Walks. 

tween  the  side  boards  at  proper  intervals  and  the  concrete 
tamped  behind  them ;  sometimes  the  concreting  is  done  in 
alternate  blocks.  When  the  steel  plate  is  withdrawn  an  open 
joint  is  left  for  expansion  and  contraction.  Where  the  plan  is 
to  lay  the  base  in  o'ne  piece  which  is  afterwards  cut  into 
blocks,  the  cutting  is  done  with  a  spade  or  cleaver. 


Fig.   117.— "Jointer"   for  Cement   Sidewalk  Work. 

Portland  cement  mortar  mixed  I  to  i^  to  I  to  2  is  used 
for  the  wearing  surface,  and  is  laid  from  l/2  in.  to  il/2  ins. 
thick,  depending  upon  the  width  of  the  walk  and  the  thickness 
of  the  base.  As  a  rule  the  mortar  is  mixed  rather  stiff;  it  is 
placed  with  trowels  in  one  coat  usually,  but  sometimes  in  two 
coats,  and  less  often  by  tamping.  The  mortar  coat  is  brought 
up  flush  with  the  top  edges  of  the  side  forms  by  means  of  the 
templet  B,  and  the  top  finished  by  floating  and  troweling. 


3io 


CONCRETE    CONSTRUCTION. 


The  wearing  coat  is  next  divided  into  sections  corresponding 
with  the  sections  into  which  the  base  is  divided,  by  cutting 
through  it  with  a  trowel  guided  by  a  straight  edge  and  then 
rounding  the  edges  of  the  cut  with  a  special  tool  called  a 
jointer  and  shown  by  Fig.  117.  An  edger,  Fig.  118,  is  then  run 
around  the  outside  edges  of  the  block  to  round  them.  The  lay- 
ing of  the  mortar  surface  must  always  follow  closely  the 
laying  of  the  base  so  that  the  two  will  set  together. 

BONDING  OF  WEARING   SURFACE  AND   BASE.— 

Trouble  in  securing  a  perfect  bond  between  the  wearing  sur- 
face and  the  base  usually  comes  from  one  or  more  of  the  fol- 
lowing causes:  (i)  Applying  the  surface  after  the  base  con- 
crete has  set.  While  several  means  are  available  for  bonding 
fresh  to  old  concrete  as  described  in  Chapter  XXIV,  the  better 


Fig.    118.— "Edger"    for   Cement   Sidewalk   Work. 

practice  is  not  to  resort  to  them  except  in  case  of  necessity 
but  to  follow  so  close  with  the  surfacing  that  the  base  will 
not  have  had  time  to  take  initial  set.  (2)  Poor  mixing  and 
tamping  of  this  base  concrete.  (3)  Use  of  clayey  gravel  "or 
an  accumulation  of  dirt  on  the  surface.  In  tamping  clayey 
gravel  the  water  flushes  the  clay  to  the  surface  and  prevents 
the  best  bond.  (4)  Poor  troweling,  that  is  failure  to  press  and 
work  the  mortar  coat  into  the  base  concrete.  Some  contract- 
ors advocate  tamping  the  mortar  coat  to  obviate  this  danger. 
Conversely,  to  make  the  surface  coat  adhere  firmly  to  the  base 
it  must  be  placed  before  the  base  concrete  has  set ;  the  base 
concrete  must  be  thoroughly  cleaned  or  kept  clean  from  sur- 
face dirtr  the  surface  coat  must  be  tamped  or  troweled 
forcibly  into  the  base  concrete  so  as  to  press  out  all  air  and 
the  film  of  water  which  collects  on  top  of  the  concrete  base. 


SIDEWALKS    AND    CURBS.  311 

PROTECTION  OF  WORK  FROM  SUN  AND  FROST. 

— Sun  and  frost  cause  scaling  and  hair  cracks.  For  work  in 
freezing  weather  the  water,  sand  and  gravel  should  be  heated 
or  salt  used  to  retard  freezing  until  the  walk  can  be  finished ; 
it  may  then  be  protected  from  further  action  of  the  frost  by 
covering  it  first  with  paper  and  then  with  a  mattress  of  saw- 
dust, shavings  or  sand  and  covering  the  whole  with  a  tar- 
paulin. Methods  of  heating  concrete  materials  and  rules  for 
compounding  salt  solutions  are  given  in  Chapter  VII.  The 
danger  from  sun  arises  from  the  too  rapid  drying  out  of  the 
surface  coating;  the  task  then  is  to  hold  the  moisture  in  the 
work  until  the  mixture  has  completely  hardened.  Portable 
frames  composed  of  tarpaulin  stretched  over  2  x  4-in.  strips 
may  be  laid  over  the  finished  walk  to  protect  it  from  the  direct 
rays  of  the  sun ;  these  frames  can  be  readily  removed  to  per- 
mit sprinkling.  Practice  varies  in  the  matter  of  sprinkling, 
but  it  is  the  safe  practice  in  hot  weather  to  sprinkle  frequently 
for  several  days.  Moisture  is  absolutely  necessary  to  the  per- 
fect hardening  of  cement  work  and  a  surplus  is  always  better 
than  a  scarcity.  In  California  the 'common  practise  is  to  cover 
the  cement  walk,  as  soon  as  it  has  hardened,  with  earth  which 
is  left  on  for  several  days. 

CAUSE  AND  PREVENTION  OF  CRACKS.— Cracks  in 
cement  walks  are  of  two  kinds,  fractures  caused  by  any  one  of 
several  construction  faults  and  which  reach  through  the  sur- 
face coating  or  through  both  surface  and  base,  and  hair  cracks 
which  are  simply  skin  fractures.  Large  cracks  are  the  result 
of  constructive  faults  and  one  of  the  most  common  of  these 
is  poor  foundation  construction  ;  other  causes  are  poor  mixing 
and  tamping  of  the  base,  too  large  blocks  for  thickness  of  the 
work,  failure  to  cut  joints  through  work.  Hair  cracks  are  the 
result  of  flushing  the  neat  cement  to  the  surface  by  excessive 
troweling  or  the  use  of  too  wet  a  mixture.  The  prevention  of 
cracks  obviously  lies  in  seeing  that  the  construction  faults 
cited  do  not  exist.  If  expansion  joints  are  not  provided,  a 
long  stretch  of  cement  walk  will  expand  on  a  hot  day  and 
bulge  up  at  some  point  of  weakness  breaking  the  walk. 

COST  OF  CEMENT  WALKS.— The  cost  of  cement  walks 
is  commonly  estimated  in  cents  per  square  foot,  including  the 
necessary  excavation  and  the  cinder  or  gravel  foundation. 


312  CONCRETE    CONSTRUCTION. 

The  excavation  usually  costs  about  13  cts.  per  cu.  yd.,  and  if 
the  earth  is  loaded  into  wagons  the  loading  costs  another  10 
cts.  per  cu.  yd.,  wages  being  15  cts.  per  hr.  The  cost  of  cart- 
ing depends  upon  the  length  of  haul,  and  may  be  estimated 
from  data  given  in  Chapter  III.  If  the  total  cost  of  excava- 
tion is  27  cts.  per  cu.  yd.,  and  if  the  excavation  is  12  ins.  deep, 
we  have  a  cost  of  I  ct.  per  sq.  ft.  for  excavation  alone.  Usu- 
ally the  excavation  is  not  so  deep,  and  often  the  earth  from  the 
excavation  can  be  sold  for  rilling  lots. 

In  estimating  the  quantity  of  cement  required  for  walks,  it 
is  well  to  remember  that  100  sq.  ft.  of  walk  I  in.  thick  require 
practically  0.3  cu.  yd.  concrete.  If  the  concrete  base  is  3  ins. 
thick,  we  have  0.3  x  3,  or  0.9  cu.  yd.  per  100  sq.  ft.  of  walk. 
And  by  using  the  tables  in  Chapter  II  we  can  estimate  the 
quantity  of  cement  required  for  any  given  mixture.  In  cement 
walk  work  the  cement  is  commonly  measured  loose,  so  that  a 
barrel  can  be  assumed  to  hold  4.5  cu.  ft.  of  cement.  If  the 
barrel  is  assumed  to  hold  4.5  cu.  ft.,  it  will  take  less  than  I  bbl. 
of  cement  to  make  I  cu.  yd.  of  1-3-6  concrete;  hence  it  will 
not  require  more  than  0.9  bbl.  cement,  0.9  cu.  yd.  stone,  and 
0.45  cu.  yd.  sand  per  100  sq.  ft.  of  3~in.  concrete  base.  The  i-in. 
wearing  coat  made  of  i-il/2  mortar  requires  about  3  bbls.  of 
cement  per  cu.  yd.,  if  the  barrel  is  assumed  to  hold  4.5  cu.  ft., 
and  since  it  takes  0.3  cu.  yd.  per  100  sq.  ft.,  I  in.  thick,  we 
have  0.3  X  3,  or  0.9  bbl.  cement  per  100  sq.  ft.  for  the  top  coat. 
This  makes  a  total  of  1.8  bbls.  per  100  sq.  ft.,  or  I  bbl.  makes 
55  sq.  ft.  of  4-in.  walk. 

As  the  average  of  a  number  of  small  jobs,  the  authors'  rec- 
ords show  the  following  costs  per  sq.  ft.  of  4-in.  walk  such  as 
just  described: 

Cts.  per  sq.  ft. 

Excavating  8  ins.  deep 0.65 

Gravel  for  4-in.  foundation,  at  $1.00  per  cu.  yd 1.20 

0.018  bbl.  cement,  at  $2.00 3.60 

0.009  cu-  yd-  broken  stone,  at  $1.50 1.35 

0.006  cu.  yd.  sand,  at  $1.00 0.60 

Labor  making  walk 1.60 

Total  cents   9.00 


SIDEWALKS    AND    CURBS. 


313 


This  is  9  cts.  per  sq.  ft.  of  finished  walk.  The  gangs  that 
built  the  walk  were  usually  two  masons  at  $2.50  each  per 
lo-hr.  day  with  two  laborers  at  $1.50  each.  Such  a  gang  aver- 
aged 500  sq.  ft.  of  walk  per  day. 

Cost  at  Toronto,  Ont. — Mr.  C.  H.  Rust,  City  Engineer,  To- 
ronto, Ont.,  gives  the  following  costs  of  constructing  concrete 
sidewalks  by  day  labor.  The  sidewalks  have  a  4-in.  founda- 
tion of  coarse  gravel  or  soft  coal  cinders,  thoroughly  consoli- 
dated by  tamping  or  rolling,  upon  which  is  placed  a  3}^-in, 
layer  of  concrete  composed  of  I  part  Portland  cement,  2  parts 
clean,  sharp,  coarse  sand,  and  5  parts  of  approved  furnace  slag, 
broken  stone  or  screened  gravel.  The  wearing  surface  is  I  in. 
thick,  or  I  part  Portland  cement,  i  part  clean,  sharp,  coarse 
sand,  and  3  parts  screened  pea  gravel,  crushed  granite, 
quartzite  or  hard  limestone.  Costs  are  given  of  a  6-ft.  and  a 
4~ft.  walk  as  follows : 

COST  OF  6  FT.  SIDEWALK. 

Per  100 
Item.  sq.  ft. 

Labor    . . $  5.59 

Cement,  1.66  bbls.,  at  $1.54 2.49 

Gravel,  2.7  cu.  yds.,  at  $0.80. 2.21 

Sand,  0.46  cu.  yd.,  at  $0.80 0.37 

Water  0.05 

Total    $10.71 

COST  OF  4  FT.  SIDEWALK. 

Per  ioo 
Item.  sq.  ft. 

Labor    . . $  6.73 

Cement,  2.04  bbls.,  at  $1.54 3-r5 

Gravel,  2.06  cu.  yds.,  at  $0.80 1.65 

Sand,  0.49  cu.  yd.,  at  $0.80 0.39 

Water    0.07 

Total ; $11.99 

The  rates  of  wages  and  the  number  of  men  employed  were 
as  follows :  i  foreman,  at  $3.50  per  day ;  i  finisher,  at  30  cts. 
per  hour;  i  helper,  at  22  cts.  per  hour;  15  laborers,  at  20  cts. 
per  hour. 


314  CONCRETE    CONSTRUCTION. 

Cost  at  Quincy,  Mass. — The  following  costs  are  given  by 
Mr.  C.  M.  Saville  for  constructing  695  sq.  yds.  of  granolithic 
walk  around  the  top  of  the  Forbes  Hill  Reservoir  embank- 
ment at  Quincy,  Mass.  This  walk  was  laid  on  a  broken  stone 
foundation  12  ins.  thick;  the  concrete  base  was  4  ins.  thick  at 
the  sides  and  5  ins.  thick  at  the  center ;  the  granolithic  finish 
was  i  in.  thick.  The  walk  was  6  ft.  wide  and  was  laid  in  6-ft. 
sections,  a  steel  plate  being  used  to  keep  adjacent  sections  en- 
tirely separate.  The  average  gang  was  6  men  and  a  team  on 
the  base  and  2  masons  and  I  tender  on  the  finish.  The  aver- 
age length  of  walk  finished  per  day  was  60  ft.  The  cost  was 
as  follows: 

Stone  Foundation  :  Per  cu.  yd.       Per  sq.  ft. 

Broken  stone  for  12-in.  foundation $  0.40  $0.015 

Labor  placing  at  15  cts.  per  hour 1.50  0.056 

Totals    $  1.90  $0.071 

Concrete  Base  4^  ins.  Thick : 

1.22  bbls.  cement  per  cu.  yd.  at  $1.53 $  1.87  $0.026 

0.50  cu.  yd.  sand  per  cu.  yd.  at  $1.02.  ...     0.51  0.007 

0.84  cu.  yd.  stone  per  cu.  yd.  at  $1.57.  . .  .      1.32  0.019 

Labor  (6  laborers,  i  team) 3.48  0.050 


Total  for  90  cu.  yds $  7.18  $0.102 

Granolithic  Finish  i  in.  Thick : 

4  bbls.  cement  per  cu.  yd.  at  $1.53 $  6.12  $0.019 

0.8  cu.  yd.  sand  at  $i 0.80  0.002 

Lampblack   0.29  o.ooi 

Labor  (2  masons,  i  helper) 6.36  0.016 


Totals    $13-57  $0.038 

The  two  masons  received  $2.25  per  day  each  and  their 
helper  $1.50  per  day,  and  they  averaged  360  sq.  ft.  per  day, 
which  made  the  cost  1^3  cts.  per  sq.  ft.  for  labor  laying 
granolithic  finish.  The  cost  of  placing  the  foundation  stone  is 
very  high  and  the  cost  of  concrete  base  also  runs  unusually 
high,  the  reasons  for  these  high  costs  are  n'ot  evident. 

Cost  at  San  Francisco. — Mr.  George  P.  Wetmore,  of  the 
contracting  firm  of  Gushing  &  Wetmore,  San  Francisco,  gives 
the  following  figures  relating  to  sidewalk  work  in  that  city 


SIDEWALKS    AND    CURBS.  3^ 

The  foundations  of  cement  walks  in  the  residence  district  of 
San  Francisco  are  2}/2  ins.  thick,  made  of  i  ~-6  concrete,  the 
stone  not  exceeding  i  in.  in  size.  The  wearing  coat  is  y2  in. 
thick,  made  of  i  part  cement  to  i  part  screened  beach  gravel. 
The  cement  is  measured  loose,  4.7  cu.  ft.  per  barrel.  The 
foundation  is  usually  laid  in  sections  10  ft.  long ;  the  width  of 
sidewalks  is  usually  15  ft.  The  top  coat  is  placed  immediately, 
leveled  with  a  straight  edge  and  gone  over  with  trowels  till 
fairly  smooth.  After  the  initial  set  and  first  troweling,  it  is 
left  until  quite  stiff,  when  it  is  troweled  again  and  polished — 
a  process  called  "hard  finishing."  The  hard  finish  makes  the 
surface  less  slippery.  The  surface  is  then  covered  with  sand, 
and  watered  each  day  for  8  or  10  days.  The  contract  price  is 
9  to  10  cts.  per  sq.  ft.  for  a  3~in.  walk;  12  to  14  cts.  for  a  4-in. 
walk  having  a  wearing  coat  %  to  i-in.  thick.  A  gang  of  3  or  4 
men  averages  150  to  175  sq.  ft.  per  man  per  day  of  9  hrs. 
Prices  and  wages  are  as  follows: 

Cement,  per  bbl $2.50 

Crushed  rock,  per  cu.  yd 1.75 

Gravel  and  sand  for  foundation,  per  cu.  yd 1.40 

Gravel  for  top  finish,  per  cu.  yd . . . . .    1.75 

Finisher  wages,  best,  per  hr 0.40 

Finisher  helper,  best,  per  hr 0.25 

Laborer,  best,  per  hr 0.20 

Cost  in  Iowa. — Mr.  L.  L.  Bingham  sent  out  letters  to  a  large 
number  of  sidewalk  contractors  in  Iowa  asking  for  data  of 
cost.  The  following  was  the  average  cost  per  square  foot  as 
given  in  the  replies : 

Cts.  per  sq.  ft. 

Cement,  at  $2  per  bbl 3-6 

Sand  and  gravel i-5 

Labor,  at  $2.30  per  day  (average) 2.2 

Incidentals,  estimated 0.7 

Total  per  sq.  ft 8.0 

This  applies  to  a  walk  4  ins.  thick,  and  includes  grading  in 
some  cases,  while  in  other  cases  it  does  not.  Mr.  Bingham 
writes  that  in  this  respect  the  replies  were  unsatisfactory.  He 
also  says  that  the  average  wages  paid  were  $2.30  per  man  per 
day.  It  will  be  noted  that  a  barrel  of  cement  makes  55,^  sq. 


CONCRETE    CONSTRUCTION. 


ft.  of  walk,  or  it  takes  1.8  bbls.  per  100  sq.  ft.     The  average 
contract  price  for  a  4-in.  walk  was  n^  cts.  per  sq.  ft. 
CONCRETE    PAVEMENT. 

Concrete  pavement  is  constructed  in  all  essential  respects 
like  cement  sidewalk.  The  sub-soil  is  crowned  and  rolled 
hard,  then  drains  are  placed  under  the  curbs ;  if  necessary  to 
secure  good  drainage  a  sub-base  of  gravel,  cinders  "or  broken 
stone  4  to  8  ins.  thick  is  laid  and  compacted  by  rolling.  The 
foundation  being  thus  prepared  a  base  of  concrete  4  to  5  ins. 
thick  is  laid  and  on  this  a  wearing  surface  2  to  3  ins.  thick. 
As  showing  specific  practice  we  give  the  construction  in  two 
cities  which  have  used  concrete  pavement  extensively. 

Windsor,  Ontario. — The  street  is  first  excavated  to  the 
proper  grade  and  crown  and  rolled  with  a  1 5-ton  roller.  Tile 


•7'0- 


-  TO"— 


Fig.  119. — Concrete  Pavement,  Windsor,  Canada. 

drains  are  then  placed  directly  under  the  curb  line  and  a 
6xi6-in.  curb  is  constructed,  using  1-2-4  concrete  faced  with 
1-2  mortar.  Including  the  3-in.  tile  drain  this  curb  costs  the 
city  by  contract  38  cts.  per  lin.  ft.  The  pavement  is  then  con- 
structed between  finished  curbs,  as  shown  by  Fig.  1 19. 

The  fine  profile  of  the  sub-grade  is  obtained  by  stretching 
strings  from  curb  to  curb,  measuring  down  the  required  depth 
and  trimming  off  the  excess  material.  The  concrete  base  is 
then  laid  4  ins.  thick.  A  1-3-7  Portland  cement  concrete  is 
used,  the  broken  stone  ranging  from  *4  m-  to  3  ins.  in  size,  and 
it  is  well  tamped.  This  concrete  is  mixed  by  hand  and  as  each 
batch  is  placed  the  wearing  surface  is  put  on  and  finished. 
The  two  layers  are  placed  within  10  minutes  of  each  other, 
the  purpose  being  to  secure  a  monolithic  or  one-piece  slab. 
The  top  layer  consists  of  2  ins.  of  1-2-4  Portland  cement  and 
screened  gravel,  %  in.  to  I  in.,  concrete.  This  layer  is  put  on 
rather  wet,  floated  with  a  wooden  float  and  troweled  with  a 


SIDEWALKS    AND    CURBS. 


317 


steel  trowel  while  still  wet.    Some  20,500  aq.  yds.  of  this  con- 
struction have  been  used  and  cost  the  city  by  contract : 

Per  sq.  yd. 

Bottom  4-in.  layer  1-3-7  concrete $0.57 

Top  2-in.  layer  1-2-4  concrete 0.32 

Excavation  ,  .  o.io 


Total $0.99 

This  construction  was  varied  on  other  streets  for  the  pur- 
pose of  experiment.  In  one  case  a  4-in.  base  of  1-3-7  stone 
concrete  was  covered  with  2  ins.  of  1-2-2  gravel  concrete.  In 
other  cases  the  construction  was :  4-in.  base  of  1-3-7  stone 
concrete;  iJ/2-in.  middle  layer  of  1-2-4  gravel  concrete,  and 
i/2-in.  top  layer  of  1-2  sand  mortar.  All  these  constructions 
have  been  satisfactory ;  the  pavement  is  not  slippery.  The 
cost  to  the  city  by  contract  for  the  three-layer  construction 
has  in  two  cases  been  as  follows : 

Church  St.,  8,000  sq.  yds. :  Per  sq.  yd. 

4-in.  base  1-3-7  concrete $0.57 

il/2-m.  1-2-4  and  V^ -in  1-2  mixture 0.32 

Excavation    o.  10 

Total    $0.99 

Albert  and  Wyandotte  Sts.,  400  sq.  yds. :  Per  sq.  yd. 

4-in.  base  1-3-7  concrete $0.66 

il/2-in.  1-2-4  and  ^2-in.  1-2  mixture 0.39 

Excavation  o.io 


Total $1.15 

The  cost  of  materials  and  rates  of  wages  were  about  as 
follows : 

Portland  cement  f.  o.  b.  cars  Windsor,  per  bbl .$2.05 

River  sand,  per  cu.  yd 1-1S 

River  gravel,  screened,  per  cu.  yd 1.25 

Crushed  limestone,  %  to  3  ins.,  per  ton 1.15 

Labor,  per  day   . . 1-75  to  2.00 

At  these  prevailing  prices  the  contractor  got  a  fair  profit  at 
the  contract  price  of  $1.15;  at  99  cts.,  any  profit  is  question- 
able, according  to  City  Engineer  George  S.  Hanes,  who  gives 


3i8  CONCRETE    CONSTRUCTION. 

us  the  above  records.    Expansion  joints  are  located  from  20  to 
80  ft.  apart  and  are  filled  with  tar. 

Richmond,  Ind. — The  first  concrete  pavement  was  built  in 
1896  and  since  then  it  has  been  used  extensively,  especially 
for  wide  alleys  and  narrow  streets  where  trafnc  is  heavy  and 
concentrated  in  small  space.  The  method  of  construction  has 
varied  from  time  to  time  but  the  construction  shown  by  Fig. 
1 20  is  fairly  representative.  Usually  a  1-3-5  concrete  is  used 
for  the  base,  5  ins.  thick,  and  a  1-2  mortar  for  the  top  coat,  il/2 
ins.  thick.  In  1904  this  pavement  cost  the  city  by  contract 
1 6  cts.  per  sq.  ft.  or  $1.54  per  sq.  yd,  with  wages  and  prices  as 
follows:  Stone  on  the  work,  $1.25  per  cu.  yd.;  gravel  and 


_ 

SSV%L^A.  HV 


S'O* A 

Fig.    120. — Concrete    Pavement,    Richmond,    Ind. 

sand,  $0.75  per  cu.  yd. ;  cement,  $2.25  per  barrel ;  common  la- 
borers, i6V2  cts.  per  hour,  and  cement  finishers,  40  cts.  per 
hour. 

CONCRETE  CURB  AND  GUTTER. 

Current  practice  varies  materially  in  constructing  concrete 
curb  and  gutter.  The  more  common  practice  is  to  lay  the 
curb  and  water  table  in  one  piece,  or  as  a  monolith,  but  this  is 
by  no  means  universal  practice.  In  much  work  the  curb  wall 
and  the  water  table  slab  are  constructed  separately,  the  con- 
struction joint  being  sometimes  horizontal  where  the  curb 
wall  sits  on  the  slab  and  sometimes  vertical  where  the  water 
table  butts  against  the  wall.  Again  it  is  the  common  practice 
to  construct  curb  and  gutter  in  sections,  laid  either  alternately 
or  in  succession,  separated  by  sand  joints  to  provide  for  ex- 
pansion and  contraction,  but  this  is  not  universal  practice, 
much  of  such  work  being  constructed  as  a  continuous  wall 
with  no  provision  for  temperature  movements  except  the  nat- 
ural breaks  at  driveways.  All  of  these  types  of  construction 
appear  to  have  given  reasonable  satisfaction,  but  exact  data 
for  a  final  comparison  are  not  available,  sq  that  we  are  forced 
to  reason  on  general  principles.  Such  a  course  of  reasoning 
indicates  that  the  best  results  should  be  expected  where  the 


SIDEWALKS    AND    CURBS. 


319 


curb  and  water  table  are  built  in  one  piece  and  in  sections  of 
reasonable  length  separated  by  expansion  joints. 

FORM  CONSTRUCTION.— The  form  construction  for 
curb  and  gutter  work  is  determined  by  the  general  plan  of 
construction  followed, — whether  monolithic  or  two-piece  con- 
struction. In  monolithic  construction  two  types  of  forms  are 
employed,  sectional  "or  box  forms  and  continuous  forms.  A 
good  example  of  box  form  is  shown  by  Fig.  121.  This  form 


Fig.  121. — Box  Form  for  Concrete  Curb1. 

was  designed  for  a  curb  14  ins.  high  at  the  back,  6  ins.  high  in 
front  and  24  ins.  from  face  of  curb  to  outer  edge  of  gutter,  con- 
structed in  sections  7  ft.  long.  The  form,  it  will  be  observed, 
is  a  complete  box,  in  which  alternate  sections  of  curb  are 
molded  and  after  having  set  are  rilled  between  using  the  same 
form  but  dispensing  with  the  end  boards  which  are  replaced 
by  the  completed  sections  of  curb.  A  fairly  representative 
example  of  continuous  form  is  shown  by  Fig.  122;  in  this  con- 


Fig.    122. — Continuous   Form   for    Concrete   Curb. 

struction  a  continuous  line  of  plank  is  set  to  form  the  back  of 
the  curb  and  another  line  to  form  the  face  of  the  gutter  slab, 
both  lines  being  held  in  place  by  stakes.  When  the  gutter 
slab  concrete  has  been  placed  and  surfaced  the  form  for  the 
front  of  the  curb  is  set  as  shown  and  the  upper  portion  of 
the  curb  wall  concreted  behind  it.  The  method  in  detail  of 
constructing  curb  and  gutter,  with  this  type  of  form,  at 
Ottawa,  Ont.,  is  described  in  a  succeeding  section.  Here  the 


320 


CONCRETE    CONSTRUCTION. 


joints  were  formed  by  inserting  a  partition  of  %-in.  boiler 
plate  every  12  ft.,  which  was  withdrawn  just  previous  to  fin- 
ishing up  the  surface;  the  sections  between  partitions  were 
concreted  continuously.  Another  method  is  to  make  the  par- 
titions of  plank,  concrete  every  other  section,  then  remove  the 
partition  plank  and  concrete  the  remaining  spaces  against  the 
previously  finished  work.  A  different  method  of  supporting 
the  plank  forming  the  face  of  the  curb  wall,  is  to  clamp  it  to 
the  back  form  (Fig.  123),  spacers  being  inserted  to  keep  the 


Fig.    123.— Continuous   Form    for   Concrete   Curb. 

two  their  proper  distances  apart.  The  forms  shown  by  Figs. 
121  to  123  are  for  monolithic  curb  and  gutter.  In  two-piece 
construction  where  the  curb  wall  is  constructed  on  the  fin- 
ished gutter  slab  practically  the  same  method  of  construction 
is  employed  as  is  illustrated  by  Fig.  122  except  that  no 
attempt  is  made  to  concrete  the  curb  wall  before  the  slab  con- 
crete has  begun  to  set.  The  more  common  and  the  preferable 
method  of  two-piece  construction  is  illustrated  by  Fig.  124; 


Fig.   124. — Form   for  Two-Piece  Curb  Construction. 

the  curb  proper  is  built  first  using  the  simple  box  form  shown 
at  the  right  hand,  then  the  water  table  is  built  using  the  com- 
pleted curb  as  the  form  for  the  back  and  a  board  held  by 
stakes  as  a  form  for  the  front.  This  board  is  set  with  its  top 
edge  exactly  to  the  grade  of  the  finished  water  table  so  as  to 
serve  as  a  guide  for  one  end  of  the  template,  the  other  end  of 


SIDEWALKS    AND    CURBS.  ;  321 

which  rides  on  the  top  of  the  finished  curb  wall.  Forms  for 
curves  at  street  intersections  are  best  constructed  by  driving 
stakes  to  the  exact  arc  of  the  curve  and  bending  a  %-in.  steel 
plate  around  them  or  bending  and  nailing  7/s  x  i^-in.  strips. 
Soaking  the  wood  strips  thoroughly  will  make  them  bend 
easily.  The  cost  of  form  work  in  constructing  curb  and  gutter 
is  chiefly  labor  cost  in  erecting  and  taking  down  the  forms. 

CONCRETE  MIXTURES  AND  CONCRETING.— The 
curb  body  is  usually  made  of  a  1-3-5  or  6  concrete  and  the 
curb  finish  of  a  1-2  mortar.  Portland  cement  is  employed 
almost  exclusively.  The  concrete  mixture  commonly  used  is 
of  such  consistency  that  thorough  ramming  is  necessary  to 
flush  the  cement  to  the  surface.  The  cubical  contents  of  com- 
bined curb  and  gutter  of  the  forms  illustrated  will  run  from 
3  to  5  cu.  yds.  per  100  ft.,  and  about  one-eighth  of  this  will 
be  facing  mortar  I  in.  thick;  thus  a  curb  running  5  cu.  yds. 
per  100  ft.  will  contain  per  100  ft.  about  0.83  cu.  yd.  of  mortar 
and  4.17  cu.  yds.  of  concrete.  The  usual  method  of  concreting 
is  to  erect  the  forms  for  the  back  of  the  curb  wall  and  the  front 
of  the  gutter  slab  and  concrete  to  the  height  of  the  water 
table  clear  across ;  then  shape  the  exposed  top  of  the  water 
table  to  section  and  place  the  mortar  finish,  and  then  erect  the 
face  form  for  the  gutter  wall,  bring  the  concrete  backing  and 
vertical  face  finish  up  together  and,  finally,  finish  the  top. 
The  finish  coat  is  placed  by  troweling  on  the  horizontal  sur- 
faces ;  on  the  vertical  face  of  the  curb  wall  it  may  be  placed  in 
any  one  of  several  ways.  Frequently  the  mortar  coat  is  sim- 
ply plastered  against  the  face  board  and  filled  behind  with 
concrete.  Another  method  is  to  lay  a  i-in.  board  against  the 
inside  of  the  form,  concrete  behind  it,  then  withdraw  the 
board,  fill  the  space  with  mortar  and  tamp  concrete  and  mor- 
tar to  a  thorough  bond.  The  special  face  forms  shown  in 
Chapter  VIII  may  be  used  in  place  of  the  board.  The  securing 
of  a  good  bond  between  the  backing  concrete  and  the  mortar 
facing  is  governed  by  the  same  conditions  that  govern  side- 
walk work. 

COST  OF  CURB  AND  GUTTER.— The  cost  of  concrete 
curb  and  gutter  is  commonly  estimated  in  cents  per  lineal  foot. 
The  cost  of  excavating,  loading  and  carting  will  run  about  the 
same  per  cubic  yard  as  for  sidewalks.  Excavating  the  trench 


322  CONCRETE    CONSTRUCTION. 

and  preparing  the  sub-grade  usually  runs  from  l/2  ct.  to  2  cts. 
per  foot  of  curb,  but  sometimes  it  amounts  to  3  cts.  Placing 
the  sub-base  will  cost  for  placing  and  tamping  i  ct.  per  it.,  to 
which  is  to  be  added  the  cost  of  materials ;  a  6-in.  sub-base 
30  ins.  wide  contains  4.7  cu.  yds.,  tamped  measure,  of  ma- 
terials per  100  ft.  The  amount  of  materials  per  foot  depends 
upon  the  cross-section  of  the  curb ;  it  equals  in  cubic  yards  the 
area  of  cross-section  in  square  feet  divided  by  27,  and  of  this 
volume  about  one-eighth  will  be  1-2  mortar  and  seven-eighths 
1-3-6  concrete.  The  tables  in  Chapter  II  give  the  amounts  of 
materials  per  cubic  yard  of  these  mixtures ;  the  product  of 
these  quantities  and  the  cost  of  the  materials  on  the  ground 
gives  the  cost.  The  labor  cost  of  mixing  and  placing,  includ- 
ing the  form  work,  will  run  from  10  to  14  cts.  per  foot.  In 
round  figures  curb  and  gutter  of  the  section  shown  in  the  ac- 
companying illustrations  may  be  estimated  to  cost  in  the 
neighborhood  of  40  cts.  per  lineal  foot.  The  following  sec- 
tions give  records  of  cost  of  individual  jobs  of  curb  and  gutter 
construction. 

Cost  at  Ottawa,  Canada. — The  method  and  cost  of  con- 
structing 1,326  ft.  of  concrete  curb  and  gutter  at  Ottawa,  Ont., 
are  given  in  some  detail  by  Mr.  G.  H.  Richardson,  Assistant 
City  Engineer,  in  the  annual  report  of  the  City  Engineer  for 
1905.  We  have  remodeled  the  description  and  rearranged  the 
figures  of  cost  in  the  following  paragraphs. 

The  concrete  curb  was  built  before  doing  any  work  on  the 
roadway,  and  the  first  task  was  the  excavation  of  a  trench  2l/2 
ft.  wide  and  averaging  I  ft.  8  ins.  in  depth  through  light  red 
sand.  On  the  bottom  of  this  trench  there  was  placed  a  founda- 
tion of  stone  spalls  8  ins.  thick;  in  width  this  foundation 
reached  from  3  ins.  back  of  the  curb  to  6  ins.  beyond  the  front 
of  the  water  table.  The  curb  was  made  5  ins.  thick  and  ran 
from  10  ins.  to  5^/2  ins.  in  height,  and  the  water  table  was  14 
ins.  wide  and  4  ins.  thick,  with  a  fall  of  ij4  ms.  from  front  to 
back.  The  concrete  used  was  a  mixture  of  I  Portland  cement, 
3  sand,  3  SHrin.  screened  limestone,  and  4  2-in.  stone.  It  was 
deposited  in  forms  and  tamped  to  bring  the  water  to  the  face 
and  then  smoothed  with  a  light  troweling  of  stiff  mortar. 

The  forms  were  constructed  by  first  setting  pickets  and  nail- 
ing to  them  a  back  board  2  ins.  thick  and  12  ins.  wide  and  a 


SIDEWALKS    AND    CURBS. 


323 


front  board  2  ins.  thick  and  6  ins.  wide.  The  concrete  for  the 
water  table  was  deposited  in  this  form  in  sections  and  brought 
to  surface  by  straight  edge  riding  on  wooden  strips  nailed 
across  the  form  and  properly  set  to  slope,  etc.  After  the  water 
table  had  been  troweled  down  and  brushed  a  I  x  lo-in.  board 
was  set  to  mold  the  front  face  of  the  curb.  This  board  was 
sustained  by  small  "knee  frames"  made  of  three  pieces  of 
i  x  2-in.  stuff,  one  conforming  to  the  slope  of  the  water  table 
and  long  enough  to  extend  beyond  the  front  of  the  2x6-in. 
front  board,  a  second  standing  plumb  and  bearing  against  the 

1  x  lo-in.  face  board,  and   the  third  forming  a   small   corner 
brace  between  the  two  former  to  hold  them  in  their  proper 
relative  positions.     The   i  x  lo-in.  face  board,  etc.,  was  sepa- 
rated from  the  2x  12-in.  back  board  by  a  5~in.  block  at  each 
end,  and  then  braced  by  the  knee  frames  every  3  or  4  ft.     In 
this  way  it  was  possible  to  bring  this  i  x  lo-in.  board  into  per- 
fect line   by   moving  the  knee  braces   in   or   out,   and  when 
correct  nailing  them  to  the  2  x  6-in.  front  board.    The  i  x  lo-in. 
face  board  being  in  position  and  braced  and  lined,  the  curb 
material  was  thoroughly  tamped  in,  and  when  ready  was  trow- 
eled and  brushed  on  the  top,  a  small  round  being  worked  onto 
the  top  front  corner  with  the  trowel. 

Expansion  joints  were  provided  for  by  building  into  the 
curb  every  12  ft.,  a  piece  of  ^-in.  boiler  plate,  which  was  after- 
ward withdrawn  and  the  joint  filled  with  sand  and  faced  over. 
As  soon  as  the  concrete  had  set  sufficiently  the  face  board  was 
taken  down  and  face  of  curb  finished  and  brushed,  the  fillet 
between  curb  and  water  table  being  finished  to  2^/2  ins.  radius. 
Circular  curb  and  gutter  of  same  construction  was  built  at 
each  corner,  l/2-in.  basswood  being  used  for  forms,  instead  of 

2  x  i -in.  lumber. 

In  addition  to  the  actual  construction  of  curb  and  gutter  the 
cost  given  below  includes  the  cleaning  up  of  the  street,  spread- 
ing or  removal  of  all  surplus  material  from  excavation,  and  the 
extension  of  all  sidewalks  out  to  the  curbs  at  the  corners.  It 
was  also  necessary  to  maintain  a  watchman  on  this  work, 
which  duty,  under  ordinary  circumstances,  would  be  done  by 
the  general  watchman.  The  total  length  built  was  1,326  ft., 
of  which  1,209  ft-  is  straight  and  117  ft.  curved  to  a  12-ft. 
radius. 


3^4 


CONCRETE    CONSTRUCTION. 


The  rates  of  wages  paid  were  $2  for  horse  and  cart,  $1.65 
for  watchman,  and  an  average  of  $1.90  per  day  for  labor,  in- 
cluding foreman ;  all  for  nine  hours'  work  per  day.  The 
working  force  consisted  of  foreman,  finisher,  handy  man.  four 
concrete  men,  and  three  laborers. 

The  labor  cost  of  the  work  was  as  follows : 

Per  ft.      P.C.-of 

Item.  Total.  cts.  total. 

Excavation  and  setting  boards. ...$  88.90  6.7  30 

Laying  stone  foundation 43-3°  3.3  14 

Concreting    61.30  4.6  20 

Finishing 45.15  3.4  15 

Carting , 9.85  0.76  3 

Watchman    25.00  1.89  8 

Clearing  up    13.60  1.04  4 

Extras  (sidewalk  extensions) I7«23  1.31  ° 

Total    $304.33           23-00  100 

The  cost  of  materials  for  curb  and  foundation  were  as 
follows : 

Per  tin.  ft 

Total.  cts. 

171.112   tons   spalls $102.93  7.76 

42  tons  2-in.  stone   41.16  3.09 

30.8  tons  ^J-in.  stone 42-57  3.21 

33,000  Ibs.  cement 161.70  12.19 

24  cu.  yds.  sand 19.20  1.45 


Total    $367-56  27,70 

The  cost  of  supplies  and  tools  was  as  follows : 

i, ocx)  ft.  B.  M.  2x12  boards  charged  off $  9.25 

500  ft.  B.  M.  2  x    6  boards  charged  off 4.12 

i ,000  ft.  B.  M.  i  x  10  boards  charged  off 14.25 

J/2-in.  basswood   4.30 

l/2  keg  3-in.  nails 1.42 

l/2  keg  4-in.  nails 1 .43 

Pickets 3.25 

Tools  charged  off 3.1 5 

Total    $41.17 


SIDEWALKS    AND    CURBS. 


325 


This  total,  when  divided  by  1,326  lin.  ft.  of  curb,  gives  the 
cost  per  lineal  foot  as  about  3  cts.  We  can  now  summarize  as 
follows : 

Per  lin.      P.  C.  of 
Item.  Total.  ft.  total. 

Labor $3°4-33  23 

Material     367.56  28 

Supplies 4I-I?  3 


43 

5i 

6 


Total    $713.06  $0.54  100 

As  indicated  above,  on  more  extensive  work  the  costs  of 
carting,  watchman,  cleaning  up,  and  extras  would  be  avoided. 
They  cost  on  this  work  5  cts.  and  the  work  could  therefore 
be  done  for  49  cts.  if  no  such  charges  were  included.  On 'such 


Fig.   125.— Concrete   Curb   and  Gutter  at  Champaign,   111. 

work  also  the  charge  for  supplies  would  be  lower  per  foot  and 
on  any  future  work  the  labor  cost  could  be  materially  lowered, 
this  curb  having  been  somewhat  of  an  experiment  as  to 
method  of  construction.  It  is  thought  that  with  no  charges 
for  carting,  cleaning,  watchman,  and  extras,  and  with  the  ex- 
perience obtained,  this  curb  could  be  built  for  about  46  cts. 
The  proportions  adopted  and  the  method  of  construction  fol- 
lowed, produce  a  very  strong,  dense,  homogeneous  curb  and 
gutter. 

Cost  at  Champaign,  111. — The  following  costs  were  recorded 
by  Mr.  Charles  Apple,  and  relate  to  work  done  at  Champaign, 
111.,  in  1903.  The  work  was  done  by  contract,  at  45  cts.  per 
lin.  ft.  of  the  curb  and  gutter  shown  in  Fig.  125. 


326  CONCRETE    CONSTRUCTION. 

The  concrete  curb  and  gutter  was  built  in  a  trench  as  shown 
in  the  cut.  The  earth  was  removed  from  this  trench  with 
pick  and  shovel  at  a  rate  of  I  cu.  yd.  per  man  per  hour.  The 
concrete  work  was  built  in  alternate  sections,  7  ft.  in  length. 
A  continuous  line  of  planks  was  set  on  edge  to  form  the  front 
and  back  of  the  concrete  curb  and  gutter ;  and  wood  partitions 
staked  into  place,  were  used.  The  cost  of  the  work  was  as 
follows : 

No.  of     Total  Cost  per 
Item.  men.      wages.    100  ft. 

Opening   trench,    18  x  3O-in 2         $3.50         $2.43 

Placing  and  tamping  cinders 2  3.50  i.oo 

Setting  forms : 

Boss  setter   I  3.00 

Assistant   setter    i  2.00 

Laborer    i  1.75 


3  $6.75         $1.69 

Mixing  and  placing  concrete : 

Clamp   man    i  $i-75 

Wheelers    3  5.25             ... 

Mixing  concrete   4  7.00 

Mixing  finishing  coat 2  3.50 

Tampers i  1.75 

Finishing: 

Foreman  and  boss  finisher i  4.00 

Assistant  finisher   i  3.00 

Water  boy   i  .50 


Total  making  concrete 14      $26.75  $7.64 

Total  for  labor  per  100  ft $12.76 

Materials  for  100  lin.  ft. :  Quantity.         Price. 

Portland  cement 8J  bbls.         $1.85  $15.42 

Cinders    7.5  yds.              .50  3.75 

Gravel    2.5  yds.            i.oo  2.50 

Broken  stone 2.5  yds.            1.40  3.50 

Sand    i.o                    i.oo  i.oo 

Total  for  material  per  100  ft $26.17 

Total  for  material  and  labor  per  100  ft $38.93 


SIDEWALKS    AND    CURBS.  327 

This  is  the  total  cost,  exclusive  of  lumber,  tools,  interest, 
profits,  etc..  and  it  is  practically  40  cts.  per  lin.  ft. 

In  100  lin.  ft.  of  curb  and  gutter  there  were  4.6  cu.  yds.  of 
concrete  and  mortar  facing,  4  cu.  yds.  of  which  were  concrete ; 
hence  the  9  men  in  the  concrete  gang  laid  14  cu.  yds.  of  con- 
crete per  day,  whereas  the  4  men  mixing  and  placing  the  mor- 
tar finishing  laid  only.  2^2  cu.  yds.  of  mortar  per  day,  assum- 
ing that  the  mortar  finishing  averaged  just  I  in.  thick.  Since 
these  4  men  (2  mixers  and  2  finishers)  received  $10.50  a  day,  it 
cost  more  than  $4  per  cu.  yd.  to  mix  and  place  the  1-2  mortar, 
as  compared  with  $1.41  per  cu.  yd.  for  mixing  and  placing  the 
concrete.  The  concrete  was  built  in  alternate  sections  7  ft. 
long.  The  3  men  placing  forms  averaged  400  lin.  ft.  a  day,  so 
that  the  cost  of  placing  the  forms  was  $i  per  cu.  yd.  of  con- 
crete. The  2  men  placing  and  tamping  cinders  averaged  16 
cu.  yds.  of  cinders  per  day,  or  8  cu.'yds.  per  man.  This  curb 
and  gutter  was  built  by  contract  at  45  cts.  per  lin.  ft. 

For  several  jobs,  in  which  a  curb  and  gutter  essentially  the 
same  as  shown  in  .Fig.  125  was  built,  our  records  show  a 
general  correspondence  with  the  above  given  data  of  .Mr. 
Apple.  Our  work  was  done  with  smaller  gangs,  I  mason  and 
2  laborers  being  the  ordinary  gang.  Such  a  gang  would  lay 
So  to  100  lin.  ft.  of  curb  and  gutter  per  lo-hr.  day,  at  the  fol- 
lowing cost : 

1  mason  at  $2.50 ' $2.50 

2  laborers  at  $1.50   3-°° 

Total    $5-5° 

This  made  a  cost  of  $l/2  to  7  cts.  per  lin.  ft.  for  labor,  and  it 
did  not  include  the  cost  of  digging  a  trench  to  receive  the  curb 
and  gutter. 


CHAPTER  XVI. 

METHODS   AND   COST  OF   LINING  TUNNELS   AND 

SUBWAYS. 

Tunnel  lining  work  is  of  two  distinct  classes :  Lining-  work 
done  during  original  construction  and  re-lining  of  tunnels  in 
service.  The  methods  of  work  to  be  adopted  and  the  cost  of 
work  will  be  different  in  the  two  cases.  In  re-lining  work  the 
costs  are  increased  by  the  necessity  of  providing  for  the  move- 
ment of  trains  and  by  the  delays  due  to  these  movements  and 
also  by  the  labor  of  removing  the  old  lining  and,  often,  of 
enlarging  the  excavation.  Comparatively  few  published  figures 


Fig.  126.— Section  Showing  Lining  for  Capitol  Hill  Tunnel,  Washington,  D.  C. 

are  available  on  the  cost  of  concrete  tunnel  lining,  and  such  as 
exist  are  commonly  incomplete.  The  common  practice  is  to 
record  the  cost  as  so  much  per  lineal  foot  of  tunnel.  This 
should  be  done,  but  the  record  should  also  show  the  cost  per 
cubic  yard  of  concrete  in  the  lining.  The  notions  of  engineers 
vary  as  to  the  proper  thickness  of  lining  to  use  and  this  di- 
mension also  varies  with  the  character  of  the  ground.  One 
tunnel  lining  may  easily  contain  twice  as  many  cubic  yards  of 
concrete  per  lineal  foot  of  lining  as  another  tunnel  contains. 

328 


TUNNELS    AND    SUBWAYS. 


329 


The  two  problems  in  form  construction  for  tunnel  work 
are :  First,  to  construct  the  form  work  so  that  it  does  not  in- 
terfere with  train  movements,  and,  second,  to  construct  it  so 
that  it  can  be  taken  down,  transported  and  re-erected  and 
thus  used  over  and  over.  The  examples  of  practice  given  in 
the  succeeding  sections  are  the  best  instructions  that  can  be 
laid  before  the  reader  in  regard  to  possible  ways  of  solving 


Plan. 

Fig.    127.— Traveling   Derrick    for    Consxructing    Side    and    Center   Walls, 
Capitol  Hill  Tunnel. 

these  problems  and,  also,  the  problem  of  handling  the  con- 
crete and  other  materials  to  the  work. 

METHOD  OF  LINING  CAPITOL  HILL  TUNNEL, 
PENNSYLVANIA  R.  R.,  WASHINGTON,  D.  C.— The  tun- 
nel through  Capitol  Hill  for  the  Pennsylvania  R.  R.  approach 
to  its  new  Union  Station  at  Washington,  D.  C.,  is  a  two- 
track,  double  tube  tunnel  4,000  ft.  long  through  earth.  Figure 


330 


CONCRETE    CONSTRUCTION. 


126  shows  the  lining  construction;  it  consists  of  stone  mas- 
onry center  wall,  mass  concrete  inverts  and  side  walls  and  a 
brick  roof  arch  backed  with  concrete.  For  building  the  center 
and  side  walls  the  traveling  derrick  shown  by  Fig.  127  was 
employed.  This  traveler  moved  ahead  with  the  work  on  a 
I4~ft.  gage  track  and  it  handled  the  stone  and  concrete  buckets 
from  the  material  cars  to  the  workmen  on  the  walls.  In  con- 
nection with  the  derrick  in  the  concrete  side  wall  construction 
use  was  made  of  steel  plate  forms  for  the  inside  faces  of  the 
walls.  These  forms  were  made  of  4x  10  ft.  sections  of  steel 
plate,  constructed  as  shown  by  Fig.  128,  and  connected  to- 
gether by  bolting  through  the  flanges.  The  steel  forms  were 
erected  by  hand  in  advance  of  the  derrick,  20  ft.  of  form  on 


Plan 


El  c  vat  ion. 


Fig.    128.—  Steel   Forms   for   Side   Walls   for   Capitcl   Hill   Tunnel. 

each  side  at  a  time.  The  concrete  buckets  were  brought  into 
the  tunnel  on  cars  hauled  by  electric  motors  from  the  mixing 
plant  at  the  portal,  and  the  buckets  were  lifted  by  the  derricks 
and  emptied  into  the  forms.  The  side  walls  were  concreted 
to  the  springing  line  and  then  the  five-ring  brick  roof  arches 
were  constructed  on  traveling  centers  and  in  2O-ft.  sections. 
The  remainder  of  the  concrete  was  then  placed  over  the 
arches  by  means  of  the  special  back-filling  machine,  shown  by 
Fig.  129.  This  machine  also  handled  the  earth  used  to  fill 
behind  the  masonry.  It  consisted  of  a  platform  mounted  on 
wheels  and  of  the  same  general  construction  as  the  derrick 
platform.  On  the  forward  end  of  this  platform  a  stationary 
hoist  was  mounted  and  behind  this  a  belt  conveyor  platform. 


TUNNELS    AND    SUBWAYS. 


331 


Fig.   129.— Device  for  Placing  Concrete  Back  Filling  for  Roof  Arch,  Capitol 

Hill   Tunnel. 


332  CONCRETE    CONSTRUCTION. 

The  latter  structure  was  pivoted  near  the  forward  end  so  that 
it  could  swing  right  and  left  on  a  circular  track amder  its  rear 
end.  It  carried  a  3O-cu.  ft.  hopper  on  its  forward  end,  from 
under  which  a  belt  conveyor  ascended  an  incline  toward  the 
rear  and  was  carried  back  into  the  space  behind  the  roof  arch 
on  a  cantilever  arm.  In  operating  the  back-filling  machine  the 
material  bucket  was  lifted  from  the  car  below,  carried  back  on 
the  trolley  beam  until  over  the  hopper  and  then  dumped  by 
hand  into  the  hopper.  From  the  hopper  the  material  dropped 
onto  the  conveyor  belt  and  was  carried  back  over  the  arch 
and  dumped  in  place  ready  for  tamping.  The  trolley  beam  of 
the  hoist  was  so  arranged  that  the  hoisting  movement  was 
vertical  until  the  bucket  hit  the  trolley  and  was  then  up  and 
backward  until  the  stop  at  the  end  of  the  trolley  beam  was 
reached.  This  point  was  directly  over  the  hopper.  Hoisting 
was  done  by  a  Lambert  engine,  driven  by  a  15  H.P.  electric 
motor.  The  conveyor  belt  was  20  ins.  wide  and  was  operated 
at  a  speed  of  180  ft.  per  minute  by  a  Jl/2  H.P.  electric  motor. 
The  machine  required  two  men  to  operate  and  was  considered 
to  save  the  labor  of  twelve  shovelers. 

METHOD  OF  CONSTRUCTING  SIDE  WALLS  IN 
RELINING  THE  MULLAN  TUNNEL.— The  Mullan  Tun- 
nel, 3,850  ft.  long,  on  the  Northern  Pacific  Ry.,  about  20  miles 
west  of  Helena,  Mont.,  had  its  original  timber  lining  replaced 
in  1894  with  a  lining  consisting  of  concrete  side  walls  and  a 
brick  roof  arch.  The  construction  of  the  old  and  new  linings 
is  shown  by  Fig.  130.  The  method  of  constructing  the  side 
walls  was  as  follows : 

The  original  timbering  consisted  of  sets  of  12  x  12-in.  posts 
carrying  five  segment  arches  of  12  x  12-in.  timbers  joined  by 
J/2-in.  dowels.  For  a  portion  of  the  lining  the  posts  carried 
plates  on  which  the  arches  set;  elsewhere  the  arches  rested 
directly  on  the  post  tops.  The  arches  and  posts  carried  4-111. 
lagging  filled  behind  with  cordwood.  The  timber  lining  was 
removed  to  make  place  for  the  new  work  in  the  manner  shown 
by  Fig.  130.  When  there  were  no  plates  a  7-ft.  section  AB 
was  first  prepared  by  removing  one  post  and  supporting  the 
undermined  arch  ribs  by  struts  5\S\  The  timbering  in  this 
section  was  cut  out  and  excavation  made  for  the  wall  footing. 
Two  temporary  posts  FF  were  then  set  up,  fastened  by  hook 


TUNNELS    AND    SUBWAYS. 


333 


bolts  L  and  lagged  behind  to  make  the  wall  form.  Several  of 
these  7-ft.  sections  were  cut  out  at  once,  each  two  being  sepa- 
rated by  a  5-ft.  section  of  timbering.  The  mortar  car  shown 
in  Fig.  130  was  then  run  alongside  the  sections  in  order  and 
enough  1-3  mortar  was  run  by  chute  into  each  to  make  an 
8-in.  layer.  As  the  car  moved  ahead  to  succeeding  sections 
enough  broken  stone  was  shoveled  into  the  last  preceding 
section  to  take  up  the  mortar.  The  walls  were  thus  built  in 
8-in.  layers  and  became  hard  enough  to  support  the  arches  in 
from  10  to  14  days.  The  arches  were  then  allowed  to  take 
footing  on  the  wall,  and  the  posts  of  the  remaining  5-ft.  sec- 
tions were  removed  and  the  concrete  wall  built  up  as  for  the 


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With  Wall  Plate.  Without  Wall  Plate. 

Section  .with  Concrete  Car.  Lonqitudinal  Section . 

Fig.    130.— Sketches    Showing   Method    of   Lining   Mullan    Tunnel. 

7~ft.  sections.  Where  the  posts  carried  wall  plates  the  struts 
5\S  were  not  needed,  the  wall  plate  supporting  the  undermined 
post  as  a  beam.  English  Portland  cement  was  used  and  the 
concrete  mixture  was  about  4  parts  mortar  to  5  parts  broken 
stone — a  very  rich  mixture.  The  average  progress  was  about 
30  ft.,  or  45  cu.  yds.  of  side  wall  per  working  day;  the  average 
cost  of  the  walls,  including  everything,  was  $8  per  cu.  yd.  of 
concrete.  The  brick  arch  cost  $17  per  cu.  yd.  Mr.  H.  C.  Relf 
is  authority  for  these  figures. 

METHOD  AND  COST  OF  LINING  A  SHORT  TUN- 
NEL, PEEKSKILL,  N.  Y.— The  following  methods  and 
costs  of  lining  a  double  track  railway  tunnel  275  ft.  long  near 


334 


CONCRETE    CONSTRUCTION. 


Peekskill,  N.  Y.,  are  given  by  Mr.  Geo.  W.  Lee.  In  presenting 
these  data  it  is  important  to  note  that  while  some  of  the 
methods  described  are  applicable  to  so  short  a  tunnel  they 
could  not  be  used  on  a  long  tunnel.  Figure  131  is  a  cross- 
section  of  the  tunnel  showing  the  lining.  The  tunnel  was 
through  rock,  which  stood  up  without  timbering,  and  the  rock 
section  was  excavated  from  6  ins.  to  3  ft.  outside  the  lining. 
A  1-2-4  concrete  using  crusher  run  stone  below  I  in.  in  size 
was  used  for  the  lining  and  portal  head  wall  coping  and  a 
1-3-6  concrete  for  the  portal  head  walls  proper.  The  cost  of 
the  portal  head  walls  is  included  in  the  costs  given  further  on. 


Figr.    131.— Cross -Section    of    Peekskill    Tunnel,    Showing    Lining. 

The  side  wall  foundation  trenches  were  first  excavated  from 
i  to  3  ft.  deep  and  footing  concreted  and  leveled  up,  the  back 
of  the  footing  being  carried  up  against  the  rock  and  the  front 
lined  to  forms  giving  a  12-in.  offset  to  the  side  wall.  The 
footings  contained  200  cu.  yds.  of  concrete.  Platforms  25  ft. 
square  and  level  with  the  springing  lines  were  then  erected  at 
each  end  of  the  tunnel.  A  derrick  was  placed  at  each  platform 
to  handle  skips  between  it  and  the  material  tracks  which  ran 
underneath  and  through  the  tunnel  with  a  turnout  at  each  end 
for  switching  back  empty  cars.  A  60  H.P.  portable  boiler 
supplied  steam  for  the  derrick  engines  and  a  pump.  The  wall 
forms  were  built  and  erected  in  panels  12  ft.  long;  these  panels 


TUNNELS    AND    SUBWAYS. 


335 


had  4  x  6-in.  plates  and  sills,  4  x  4-in.  studs  3  ft.  on  centers  and 
2-in.  dressed  and  matched  spruce  sheeting.  Four  panels  were 
set  up,  two  on  each  side,  midway  of  the  tunnel  and  braced  to 
the  tunnel  track.  Wheelbarrow  runways  carried  on  bents 
were  built  from  the  platforms  to  the  forms,  one  from  one  plat- 
form to  one  side,  another  from  the  other  platform  to  the  op- 
posite side.  Temporary  bulkheads  were  erected  to  close  the 
ends  of  the  forms  and  they  were  filled.  Meanwhile  carpenters 
were  setting  other  panels  at  each  end  of  the  two  first  erected 
on  each  side.  After  24  hours  the  panels  first  set  were  taken 
down  and  moved  ahead  and  the  processes  described  continued 
until  the  full  length  of  side  wall  was  completed.  The  side 
walls  were  not  concreted  back  to  the  rock;  back  forms  of  i-in. 
hemlock  were  used  and  the  space  remaining  was  filled  with 
spalls.  The  side  walls  contained  692  cu.  yds.  of  concrete. 

Arch  forms  were  erected  for  96  ft.  at  the  center  of  the 
tunnel,  using  12-ft.  lagging,  so  that  sections  of  this  length 
could  be  taken  down  and  moved  ahead,  nine  at  each  end.  The 
lagging  was  first  laid  to  a  height  of  3  ft.  above  the  springing 
line  on  each  side  and  the  concrete  dumped  directly  in  place 
from  runways  laid  on  the  lower  chords  of  the  arch  ribs,  which 
were  placed  4  ft.  apart.  When  the  concrete  reached  a  height 
too  great  for  direct  discharge  into  the  forms  it  was  dumped  on 
the  runway  and  passed  over  with  shovels.  On  the  upper  por- 
tion of  the  ring  the  concrete  was  first  shoveled  to  a  platform 
erected  on  the  center  posts  of  the  ribs  about  2  ft.  below  the 
crown  and  then  passed  in  on  the  lagging  which  was  laid  in 
4-ft.  instead  of  12-ft.  lengths  at  this  stage  of  the  work.  As 
soon  as  each  section  of  arch  ring  was  completed  it  was  water- 
proofed with  six  layers  of  tar  paper  laid  in  hot  tar  and  then 
packed  behind  with  spalls.  The  arch  centers  were  struck  in 
a  comparatively  short  time ;  in  one  instance  they  were  struck 
90  hours  after  the  last  concrete  was  placed  and  no  settlement 
was  apparent.  The  arch  forms  stuck  so  fast  to  the  concrete, 
however,  that  they  had  to  be  jacked  down  by  chiseling  out  the 
lagging  so  as  to  get  a  bearing  on  the  arch  concrete  and  by 
nailing  thrust  blocks  to  the  rib  posts.  The  section  was  then 
hauled  ahead  by  passing  the  main  fall  of  the  derrick  through 
a  snatch  block  on  the  first  rib.  When  hauled  clear  of  the  lin- 
ing all  but  the  first  3-ft.  of  lagging  on  each  side  was  removed ; 


336  CONCRETE    CONSTRUCTION. 

they  were  then  jacked  into  position.    The  arch  ring  contained 
932  cu.  yds.  of  concrete. 

Including  the  portal  head  walls  1,948  cu.  yds.  of  concrete 
were  laid  at  the  following  costs  for  labor  and  materials : 

Item.                                                              Total.  Per  cu.  yd. 

Cement  at  $1.63  per  bbl $  5,755.50  $2.951 

Sand  at  $0.75  per  cu.  yd 662.94  °-339 

Stone  at  $0.80  per  cu.  yd 1,303.20  0.668 

Lumber — 

Mixing  platforms  and  runways 336.89  0.174 

Ribs,  including  hand  sawing 234.10  0.120 

Backing  boards   134-44  0.069 

Lagging .        341.04  0.176 

Sheathing    268.49  ai37 

Plates,  sills,  studs,  braces l&2-75  °-°93 

Coal    1 18.73  0.06 1 

Oil    16.12  0.008 

Hardware,  nails,  spikes,  etc 224.39  0.118 

Tools    181.10  0.093 

Freight  on  stone,  cement,  etc 3,089.86  1.584 

Labor  of  all  kinds 8,036.31  4.121 


Total    $20,885.86  $10.712 

METHOD  OF  LINING  CASCADE  TUNNEL,  GREAT 
NORTHERN  RY.— The  Cascade  Tunnel,  13,813  ft.  long,  built 
in  1897-1900,  was  lined  throughout  with  concrete  from  24  ins. 
to  $}/2  ft.  thick,  mixed  and  placed  in  the  following  manner: 
It  was  necessary  to  place  the  lining  without  interfering  with 
the  transportation  of  materials  and  excavated  material  to  and 
from  the  work  ahead.  The  arrangement  adopted  to  secure 
this  end  is  shown  by  Fig.  132.  A  platform  500  ft.  long  was 
constructed  at  the  elevation  of  the  wall  plates ;  the  rear  end  of 
this  platform  was  reached  by  an  incline,  up  which  the  cars 
loaded  with  concrete  were  hauled  by  an  air  hoist  and  cable 
and  delivered  to  any  point  on  this  platform.  While  each  500 
ft.  of  tunnel  was  being  concreted,  the  next  500  ft.  of  platform 
in  advance  was  being  built,  with  its  approach  incline,  so  that 
there  was  no  delay  in  the  work. 

Complete  concrete  plants  were  installed  at  each  portal,  ad- 
vantage being  taken  of  the  side  hills  of  the  approach  into  the 


TUNNELS    AND    SUBWAYS. 


337 


mountain  to  handle  as  much  ma- 
terial as  possible  by  gravity. 
Each  plant  was  equipped  with  a 
No.  6  Gates  crusher,  4O-in.  x  8-ft. 
rock  screens,  and  i6-in.  x  i6-ft. 
screw  concrete  mixers.  Large 
storage  bins  for  the  cement,  sand 
and  stone  were  built  adjacent  tq 
the  mixer  plant.  A  1-3-5  concrete 
was.  used.  The  stone  was  crushed 
from  the  best  rock  obtained  in  the 
tunnel  excavation.  This  rock  was 
loaded  into  the  regular  muck  cars, 
taken  to  the  portal  by  electric 
motors,  and  then  dumped  into 
other  cars  below  the  lever  of  the 
muck  cars.  These  cars  were 
hauled  by  hoisting  engine  and 
cable  to  the  crusher  floor  and  then 
dumped  and  sorted  to  avoid  dan- 
ger from  pieces  of  unexploded 
dynamite.  It  was  then  run 
through  the  crushers,  washers 
and  screens  to  the  stone  bin  and 
thence  to  the  mixers.  The  mixed 
concrete  was  discharged  into  cars 
on  the  level  of  the  muck  car 
tracks  and  these  cars  were  taken 
by  motor  into  the  tunnel  to  the 
incline,  up  which  they  were 
hauled  by  cable  and  dumped  on 
the  platform.  From  the  platform 
the  concrete  was  shoveled  into 
the  wall  forms  or  onto  the  centers 
as  desired. 

The  walls  were  concreted  in  al- 
ternate 12-ft.  sections,  the  weight 
on  the  timber  arch  thus  being 
gradually  transferred  from  the  plumb  posts  to  the  walls.  The 
roof  arch  was  also  built  in  12-ft.  sections,  the  centers  being 


Fig.  .132.— Traveling    Platform 

Used    in    Lining    Cascade 

Tunnel. 


338 


CONCRETE    CONSTRUCTION. 


in  sections  of  corresponding  length  which  were  moved  forward 
on  dollies  and  jacked  up  as  trie  work  advanced.  Ten  sections 
of  centering  were  used  at  each  end.  An  average  of  7  bbls.  of 
cement  were  used  per  lineal  foot  of  lining.  The  average 
monthly  progress  of  lining  was  about  600  ft.  at  each  end.  The 
concrete  lining  cost  $44  per  lin.  ft.  of  tunnel,  done  by  company 
forces. 

METHOD  OF  RELINING  HODGES  PASS  TUNNEL, 
OREGON  SHORT  LINE  RY.— The  centers  and  side  wall 
forms  and  the  methods  of  work  adopted  in  relining  the  Hodges 
Pass  tunnel  on  the  Oregon  Short  Line  Ry.  are  explained  in 
the  accompanying  illustrations.  This  tunnel  is  1,425.8  ft.  long 


_BSJ ssj isi — _M Bf        sa        tsa        ^i 


£/// 


-fbsts" 


Finished  firr+      ExcaYartierj  &  Bridge 
Plan. 


Longi+udinail      Section. 
Fig.  133.— Method  of  Placing  Invert  Concrete,  Hodges'  Pass  Tunnel. 

and  when  constructed  in  1882  was  lined  with  timber.  The 
new  lining  consists  of  concrete  side  walls  carrying  a  brick  roof 
arch.  Both  the  old  and  the  new  linings  are  shown  in  the 
drawings.  The  tunnel  is  through  a  variety  of  rock  and  clay 
strata,  and  through  the  soft  strata  an  invert  was  required. 
Altogether  about  one-third  of  the  length  of  the  tunnel  was 
provided  with  an  invert.  It  will  be  noted  also  that  the  new 
lining  occupies  materially  more  space  than  the  old ;  this  made 
necessary  considerable  excavation  in  enlarging  the  section. 

The  work  of  relining  consisted  of  three  operations,  viz.,  the 
invert  construction,  the  construction  of  the  side  walls  and  the 
arch  construction. 


TUNNELS    AND    SUBWAYS. 


339 


The  form  of  the  invert  is  shown  in  Fig.  136.  It,  of  course, 
had  to  be  constructed  without  entailing  a  break  in  the  track, 
and  the  method  adopted  was  as  follows :  The  ties  and  ballast 
were  removed  from  a  section  oi  track  about  12  ft.  long  and 


in  their  place  was  substituted  the  timber  frame  shown  in  Fig. 
133.  Under  the  middle  portion  of  this  frame  a  trench  reach- 
ing clear  across  the  tunnel  and  having  a  width  of  6  to  7  ft.  in 
the  direction  of  the  track  was  excavated  to  subgrade  of  the 


340 


CONCRETE    CONSTRUCTION. 


invert.  The  concrete  was  filled  into  this  trench,  formed  to 
shape  on  top,  and  allowed  to  harden.  The  bridging  frame  was 
then  taken  out  and  the  ties  and  ballast  were  replaced.  Another 
section  of  track  was  then  bridged,  trenched  and  concreted  and 
so  on  until  the  length  of  invert  required  was  constructed. 


Fig.   135.— Side  Wall  Forms  for  Plans  A  and  B,  Fig.   134. 

The  side  wall  construction  was  a  more  complex  operation. 
It  comprised  first  the  removal  of  the  old  lining,  the  enlarging 
excavation  and  the  form  erection  and  concreting.  Two  meth- 
ods of  performing  this  task  were  employed.  Both  are  illus- 
trated in  Fig.  134.  By  the  first  method,  designated  as  Plan  A, 
the  concreting  was  done  continuously  in  sections  of  consider- 


TUNNELS    AND    SUBWAYS. 


341 


able  length.  The  forms  used  are  shown  in  detail  by  Fig.  135. 
By  the  second  method,  the  concreting  was  done  in  alternate 
short  panels.  This  method  is  designated  Plan  B  on  the  draw- 
ings, Fig.  134.  The  forms  used  are  shown  in  detail  by  Fig. 
135.  The  only  difference  in  the  form  construction  for  the  two 
plans  is  in  the  connection  of  the  posts  at  the  top. 

The  construction  of  the  centering  for  the  roof  arch  is  shown 
by  Figs.  136  and  137,  Fig.  137  giving  detail  dimensions  of  the 
ribs  and  lagging.  The  center,  as  shown  by  Fig.  136,  consisted 
of  four  ribs  spaced  3  ft.  on  centers.  Each  rib  consists  of  two 
side  posts  and  an  arch  piece.  The  side  posts  on  each  side  are 


-.    j    fhck  Section 
Plan  "A'.'  .PI an  «&'!..  Cross    Section. 

Fig.   136. — General  Plan  of  Centers  for  Roof  Arch,  Hodges'  Pass  Tunnel. 

connected  at  the  bottoms  by  a  sill  and  at  the  top  by  a  cap. 
Jacks  between  the  sill  and  a  mud  sill  laid  on  the  concrete  in- 
vert or  in  the  ditch  held  the  center  in  place  during  arch  con- 
struction. Lowering  these  jacks  dropped  the  center  onto 
trucks  traveling  on  the  mud  sills.  Thus  the  center  was  moved 
along  as  the  work  progressed.  As  will  be  noted  from  Figs. 
134  and  135,  the  side  wall  forms  carried  the  work  only  to  the 
bottoms  of  the  old  caps.  The  arch  center  completed  the  con- 
crete wall  work  and  the  roof  arch.  Only  about  one-third  of 
the  new  lining  had  the  brick  arch,  as  shown  by  the  drawings; 


342 


CONCRETE    CONSTRUCTION. 


A & 


|^~~""  ~  ""     W        MT 

Fig.    187.— Detail!  of  Centers  for  Roof  Arch.  Hodges'  Pass  TunneL 


TUNNELS    AND    SUBWAYS.  343 

in  the  remaining  two-thirds  the  concrete  was  carried  up  much 
further  on  each  side ;  in  fact,  the  brickwork  constituted  only 
the  top  third  of  the  arch. 

In  describing  the  forms  and  centers  we  have  left  much  of 
the  explanation  to  the  drawings.  These  show  all  dimensions 
and  details,  and  indicate  in  a  measure  the  mode  of  procedure. 
The  work  done  consisted  of  excavation  enlarging  the  section, 
of  removing  the  old  timber  lining  and  of  the  form  work,  con- 
creting and  bricklaying  for  the  new  lining.  All  of  it  above 
convenient  reach  from  the  ground  was  done  from  a  movable 
staging  formed  by  a  deck  fixed  on  a  flat  car  so  as  to  be  ad- 
justable in  height.  The  concrete  was  mixed  by  hand  on  this 
car  platform  and  shoveled  directly  into  the  forms,  the  platform 
being  raised  as  the  work  increased  in  height.  The  concrete 
used  was  a  1-3-5  mixture  of  2^ -in.  broken  stone. 

The  organization  of  the  working  force  is  not  easily  stated 
since  the  work  was  done  as  the  traffic  permitted  and  varied 
with  the  conditions.  Generally  from  12  to  16  men  were  all 
that  could  be  employed  to  advantage.  Complete  records  of 
cost  were  kept,  but  they  were  destroyed  by  fire,  so  that  the 
only  figures  available  on  this  point  are  the  totals.  These  are 
as  follows: 

Item.  Totals.  Per  lin.  ft. 

Labor  $21,129  $14.81 

Materials    .1 13,939  977 


Total    $35.o68  $24-58 

These  amounts  average  the  cost  of  the  invert,  which  was 
required  for  about  one-third  of  the  length,  over  the  whole  tun- 
nel. 

RELINING  A  SHORT  TUNNEL.— The  following  figures 
show  the  cost  of  relining  with  concrete  a  timber  lined  railway 
tunnel.  The  concrete  side  walls  were  14  ft.  high  and  had  an 
average  thickness  of  2^2  ft.  Therefore  each  side  wall  averaged 
nearly  1.3  cu.  yds.  per  lin.  ft.,  and  the  two  walls  averaged  2.59 
cu.  yds.  per  lin.  ft.  of  tunnel.  The  concrete  was  mixed  1-3-5, 
being,  we  believe,  unnecessarily  rich  in  cement.  The  average 
amount  of  concrete  placed  in  the  walls  per  day  was  50  cu.  yds. 


344  CONCRETE    CONSTRUCTION. 

Cost  of  Side  Walls. 
Materials —  Per  cu.  yd. 

1.33  bbl.  cement  at  $2.00 $2.66 

0.5    cu.  yd.  sand  at  0.18 0.09 

0.75  cu.  yd.  stone  at  0.55 0.41 

Total    $3.16 

Labor  on  concrete — 

o.oi  day  foreman  at  $5.00 $0.05 

0.03  day  foreman  at  $3.00 0.09 

0.03  day  engineman  at  $3.00 0.09 

0.35  day  laborer  at  $1.75 0.61 


0.42      Total    $0.84 

Labor,  removing  timber,  building  forms,  excavating,  etc. — 

0.02  day  foreman  at  $5.00 $0.10 

0.05  day  foreman  at  $3.00 0.15 

0.40  day  laborer  at  $1.75 0.70 

0.47      Total   $0.95 

Miscellaneous — 

0.02  day  engineer  and  superintendent  at  $5.00 $0.10 

Falsework  and  forms,  timber  and  iron 0.07 

Tools,  light,  etc o.io 

Interest  and  depreciation  of  $1,800  plant  at  20%  per  an- 
num      0.09 

Train  service,  0.03  day  work  train  at  $25 0.75 

Summary  concrete  side  walls —  Per  cu.  yd. 

Materials    $3.16 

Labor  on   concrete 0.84 

Labor  removing  timber,  etc 0.95 

Train   service    0.75 

Miscellaneous   0.34 

Total   * $6.04 

In  the  two  side  walls  there  were  2.59  cu.  yds.  of  concrete 
per  lin.  ft.  of  tunnel,  hence  the  cost  of  the  side  walls  was 
$6.04  X  $2.59  —  $15.64  per  lin.  ft.  of  tunnel. 


TUNNELS    AND    SUBWAYS. 


345 


The  concrete  arch  varied  in  thickness,  averaging  from  14  to 
20  ins.  at  the  springing  line  to  8  to  14  ins.  at  the  crown.  The 
arch  averaged  1.2  cu.  yds.  per  lin.  ft.  of  tunnel.  About  20  cu. 
yds.  of  arch  were  placed  per  day.  The  arch  concrete  was 
mixed  1-3-5  and  the  cost  was  as  follows : 

Cost  of  Concrete  Arch. 
Materials —  Per  cu.  yd. 

1.36  bbls.  cement,  $2.00 $2.72 

0.05  cu.  yd.  sand,  0.18 0.09 

0.75  cu.  yd.  stone,  0.55 0.41 

Total    $3.22 

1.8  cu.  yds.  dry  rock  backing  at  0.55 $0.99 

Labor  on  concrete — 

0.02  day  foreman  at  $5.00 '.  . .  .$0.10 

o.i  2  day  foreman  at     3.00 0.36 

0.88  day  laborer   at      1.75 1.54 

1.02      Total    $1.96 $2.00 

Labor  placing  1.08  cu.  yds.  rock  backing — 

o.oi  day  foreman  at  $5.00 $0.05 

0.51  day  foreman  at     3.00 0.15 

0.55  day  laborer   at      1.75 0.96 


0.61      Total    $1.90 $1.16 

Labor  removing  timbers,  forms,  excavations,  etc. — 

0.02  day  foreman  at  $5.00 $0.10 

0.04  day  foreman  at     3.00 0.12 

0.06  day  carpenter  at    2.50 * 0.15 

0.40  day  laborer    at      1.75 0.70 


0.52      Total    $2.06 $1.07 

Train  service — 
0.06  day  at  $25 $i  .50 

Miscellaneous — 

Engineering   and   superintendence 07 

Falsework,  timber  and  iron 13 

Tools,  light,  etc 12 

Interest  and  depreciation,  $1,800  plant,  20%  per  annum.  .   0.09 


346  CONCRETE    CONSTRUCTION. 

Summary  concrete  arch —  Per  cu.  yd. 

Concrete  materials $3-22 

Dry  rock  backing  (1.8  c.  y.) °-99 

Labor  and  concrete 2.00 

Labor  placing  1.8  cu.  yds.  rock  backing 1.16 

Labor  removing  timber,  etc 1.07 

Train  service  hauling  materials 1.50 

Engineering  and  superintendence 0.07 

Falsework,  timber  and  iron 0.13 

Tools,  light,  etc o.  1 2 

Interest  and  depreciation  plant 0.09 

Grand  total  $10.35 

It  will  be  noted  that  the  ''train  service"  is  an  item  that  really 
should  be  considered  as  a  part  of  the  cost  of  the  materials,  for 
the  cost  of  the  sand  and  stone  is  the  cost  f.  o.  b.  cars  at  the 
sand  pit  and  at  the  quarry,  to  which  should  be  added  the  cost 
of  hauling  them  to  the  tunnel — to-wit,  the  "train  service." 

Summing  up,  we  have  the  following  as  the  cost  per  lineal 
foot  for  lining  this  single-track  tunnel  with  concrete : 

Per  lin.  ft. 

2.59  cu.  yds.  side  walls  at  $6.04 $15.64 

1.20  cu.  yds.  arch  at  10.33 12.40 


3.79  cu.  yds.     Total    $9.38 $28.04 

It  should  be  remembered  that  the  higher  cost  of  the  arch 
concrete  is  due  in  large  measure  to  the  fact  that  1.8  cu.  yds.  of 
dry  rock  packing  above  the  arch  are  included  in  the  cost  of  the 
concrete.  Strictly  speaking,  this  dry  rock  packing  should  not 
be  charged  against  the  arch  concrete,  and,  segregating  it,  we 
have  the  following: 

2.59  cu.  yds.  concrete  side  walls  at $6.04 

1. 20  cu.  yds.  concrete  arch  at 8.18 

2.16  cu.  yds.  dry  rock  at 0.55 

Labor  placing  2.16  cu.  yds.  at 0.64 

Total $28.04 

This  is  a  much  more  rational  analysis  of  the  cost  and  a  still 
further  reduction  in  the  cost  of  the  arch  concrete  might  be 


TUNNELS    AND    SUBWAYS. 


347 


made  by  prorating  the  train  service  item  ($1.50  per  cu.  yd. 
concrete).  At  least  half  of  this  train  service  should  be  charged 
to  the  dry  rock  backing,  for  there  are  1.25  cii.  yds.  of  sand  and 
broken  stone  to  1.80  cu.  yds.  of  dry  rock  backing. 

The  amount  of  this  dry  rock  backing,  or  packing,  varies 
greatly  in  different  parts  of  a  tunnel.  In  the  first  half  of  this 
tunnel  it  averaged  1.8  cu.  yds.  per  lin.  ft.,  while  in  the  second 
half  it  averaged  nearly  2.4  cu.  yds.  per  lin.  ft. 

METHOD  OF  MIXING  AND  PLACING  CONCRETE 

FOR  A  TUNNEL  LINING.— The  tunnel  known  as  the  Bur- 


Fig.   138. — Sections  Showing  Concrete  Lining  for  Burton  Tunnel. 

ton  tunnel  is  located  on  the  Jasper-French  Lick  extension  of 
the  Southern  Ry.,  and  about  4  miles  from  French  Lick,  Ind. 
It  is  a  single  track  tunnel  2,200  ft.  long  with  300  ft.  at  one  end 
on  a  4°-3o'  curve  and  1,900  ft.  on  tangent.  The  material  pene- 
trated was  slate  and  loose  rock,  requiring  solid  timbering 
throughout.  This  timbering  is  shown  by  Fig.  138,  which  also 
shows  the  concrete  lining;  the  timbering  was  embedded  in  the 
concrete  lining. 

The  original  timber  lining  was  composed  as  follows:    Posts 
IQX  12  ins.  and  spaced  3  ft.  apart  were  set  on  3  x  12-in.  sills 


348 


CONCRETE    CONSTRUCTION. 


and  carried  ioxi2-in.  wall  plates  which  supported  ioxi2-in. 
segmental  arch  ribs  spaced  3  ft.  apart.  The  lagging  behind 
the  posts  was  3  x  6-in.  stuff  and  the  lagging  over  the  arch  ribs 
was  4  x  6-in.  stuff.  The  section  of  the  concrete  lining  is  shown 
by  Fig.  138,  it  required  4.132  cu.  yds.  of  concrete  and  161.43 
Ibs.  of  reinforcement  per  lin.  ft.  The  concrete  was  a  1-2^2-5 
crushed  stone — between  2  in.  and  y\  in.  size — mixture;  it  re- 
quired 1.16  bbls.  of  cement,  0.52  cu.  yds.  sand  and  0.92  cu.  yds. 


Fig.    13?.— View    of   Mixer   Plant   Showing   Car    Tracks,    Burton    Tunnel. 

of  stone  per  cubic  yard  of  concrete.    The  amount  of  reinforce- 
ment per  cubic  yard  of  concrete  was  39.1  Ibs. 

All  the  concrete  was  mixed  and  handled  from  one  end  of  the 
tunnel.  The  mixing  plant  was  located  in  the  approach  cut  at 
one  end.  A  standard  gage  main  track  ran  through  the  cut. 
About  20  ft.  in  the  clear  to  one  side  of  this  track  a  trestle  500 
ft.  long  was  built,  carrying  an  i8-ft.  gage  derrick  track  and  a 


TUNNELS    AND    SUBWAYS. 


349 


narrow  gage  3-cu.  yd.  dump  car  track.  A  stiff  leg  derrick 
operating;  a  I  cu.  yd.  orange  peel  or  a  il/2  cu.  yd.  clam-shell 
Hayward  bucket  was  mounted  on  a  carriage  traveling  on  the 
iS-ft.  gage  track.  The  side  of  the  trestle  nearest  the  railway 
track  was  sheeted  vertically  and  the  space  between  this  sheet- 
ing and  the  track  was  floored  over  at  track  level  for  stock 
piles.  Near  the  end  of  the  trestle  toward  the  tunnel  and  on 
the  same  side  of  the  track  was  the  mixer  plant.  This  con- 
sisted of  two  85  cu.  yd.  bins,  one  for  sand  and  one  for  stone, 
carried  by  a  tower  so  that  their  bottoms  were  25  ft.  above 


Fig.    140, — View    of   Mixer    Plant    Showing   Method    of    Unloading    Materials, 

Burton  Tunnel. 

track  level.  Below  the  bins  was  a  charging  platform  pierced 
by  a  measuring  hopper.  Below  the  measuring  hopper  was  a 
1*2  cu.  yd.  cubical  mixer  and  below  the  mixer  was  a  3-ft.  gage 
track  for  il/2  cu.  yd.  Koppel  side  dump  cars.  To  the  rear  of 
the  tower  at  ground  level  there  was  a  2O-cu.  yd.  sand  bin  and 
a  2O-cu.  yd.  stone  bin  set  side  by  side  with  a  continuous  bucket 
elevator  leading  from  each  to  the  corresponding  bin  on  the 
tower.  The  cement  house  was  located  directly  across  the  rail- 
way track  from  the  tower.  At  the  side  of  the  cement  house 
nearest  the  track  there  was  an  inclined  bag  elevator  leading 


350  CONCRETE    CONSTRUCTION, 

up  to  a  bridge  spanning  the  railway  track  at  the  level  of  the 
charging  floor  of  the  mixer  plant.  On  this  bridge  san  a  car 
for  carrying  bags  of  cement.  The  plant  as  described  is  shown 
by  Figs.  139  and  140. 

In  operation  the  derrick  unloaded  the  stone  and  sand  cars 
by  means  'of  the  Hayward  buckets  either  into  the  bins  at  the 
feet  of  the  bucket  elevators  or  onto  stock  piles  on  the  flooring 
beside  the  trestle.  When  put  into  stock  piles  the  materials 
had  to  be  reloaded  by  derrick  into  the  3  cu.  yd.  cars  on  the 
trestle  narrow  gage  track  and  carried  by  these  cars  to  the  ele- 
vator boots.  The  sand  and  stone  were  chuted  from  the  tower 
bins  directly  into  the  charging  hopper  below.  Here  the  cement 
bags,  brought  across  the  bridge  on  the  car  into  which  they 
were  loaded  directly  by  the  bag  elevator,  were  opened  and  the 
cement  added  to  the  sand  and  stone.  The  charge  was  then 
dropped  into  the  mixer  and  from  the  mixer  the  batch  dropped 
into  the  Koppel  concrete  cars. 

In  the  tunnel  a  traveling  platform  was  constructed  on  two 
standard  gage  flat  cars  so  coupled  that  a  platform  100  ft.  long 
and  slightly  narrower  than  the  clear  space  between  side  wall 
forms  was  obtained.  Connecting  the  end  of  the  platform 
toward  the  mixing  plant  was  a  rampe  or  inclined  platform 
mounted  on  wheels.  The  Koppel  car  tracks  from  the  mixer 
were  carried  up  the  incline  and  the  full  length  of  the  level  plat- 
form. The  cars  were  hauled  to  the  foot  of  the  incline  by  a 
light  locomotive.  A  cable  was  then  hooked  to  them ;  this 
cable  was  run  through  a  block  on  the  level  platform,  its  free 
end  coming  back  to  the  locomotive,  which  thus  pulled  the  cars 
up  the  incline  by  moving  back  toward  the  mixer.  On  the  level 
platform  the  cars  were  pushed  by  hand  and  dumped  on  the 
floor,  whence  the  concrete  was  shoveled  into  the  forms. 

The  platform  construction  deserves  mention  in  the  particu- 
lar that  it  provided  for  adjusting  the  platform  vertically.  At 
each  corner  of  the  car  a  vertical  post  some  7  or  8  ft.  high  was 
set  up.  The  side  stringers  of  the  platform  carried  two  vertical 
posts  at  each  end ;  these  two  posts  were  spaced  just  far  enough 
apart  to  slide  over  the  corner  post,  one  on  each  side  of  it.  A 
block  at  the  top  of  the  corner  posts  with  the  hoist  line  con- 
nected to  the  bottoms  of  the  platform  posts  and  the  lead  line 
going  to  a  winch  head,  thus  made  it  possible  to  lift  the  plat- 


TUNNELS    AND    SUBWAYS. 


351 


form  any  distance  within  the  height  of  the  vertical  post  guide 
and  hold  it  there  by  blocking  under  the  posts.  The  arrange- 
ment is  shown  roughly  by  the  sketch,  Fig.  141.  There  was 
block  and  tackle  for  each  corner  post  and  a  winch  at  each  end 
of  the  car.  The  vertical  movement  of  the  platform  was  be- 
tween 6  and  7  ft. 

The  floor  was  cemented  first,  then  the  side  walls  and  finally 
the  roof  arch.  Floor  construction  was  begun  at  the  portal 
farthest  from  the  mixing  plant.  Koppel  car  tracks  were  laid 
through  the  tunnel  and  the  concrete  was  dumped  from  them 
directly  on  the  ground.  The  cars  were  hauled  by  a  light  loco- 
motive. As  the  concreting  advanced  the  dump  car  track  was 
raised  and  suspended  from  timbers  across  tunnel  so  that  the 


Fig. 


Ena-Contr 


141.— Sketch    Showing  Telescopic   Support   for  Concreting   Platform, 
Burton   Tunnel. 


concrete  could  be  placed  under  it.  As  fast  as  the  floor  hard- 
ened the  permanent  standard  gage  track  was  laid  and  a  tem- 
porary third  rail  placed  to  give  also  a  dump  car  track. 

When  the  floor  had  been  finished  the  side  walls  were  con- 
structed, using  the  traveling  platform  and  beginning  at  the  far 
portal.  The  wall  forms  consisted  of  4  x  6-in.  studs,  spaced  3  ft. 
apart  and  carrying  2x  12-in.  lagging.  A  6  x  6-in.  waling  out- 
side the  studs  at  about  mid-height  held  the  studs  to  the  tim- 
bering by  lag  bolts  reaching  through  the  wall  to  the  lox  12-in. 
posts.  A  strip  of  plank  nailed  across  wall  between  stud  and 
post  held  the  form  at  the  top.  Wall  forms  were  erected  for 
100  ft.  of  wall  at  a  time.  These  forms  required  about  45  ft. 


352 


CONCRETE    CONSTRUCTION. 


B.  M.  lumber  per  lineal  foot  of  form  on  one  side  or  90  ft.  B.  M. 
for  both  sides.  Two  sets  of  side  wall  forms  or  200  ft.  of  wall 
forming  were  built,  and  used  over  and  over  again.  The  con- 
crete was  shoveled  into  the  wall  forms  from  the  traveling  plat- 
form, the  lagging  being  placed  a  board  at  a  time  as  the  work 
progressed  upward  and  the  platform  being  elevated  as  re- 
quired, its  final  position  being  at  about  springing  line  level. 
When  100  ft.  of  side  walls  had  been  completed  the  traveling 
platform  was  moved  ahead  for  another  loo-ft.  section. 

The  centers  consisted  of  6x  12-in.  ribs,  made  up  of  3  x  12-in. 
plank.  The  feet  of  the  ribs  rested  on  folding  wedges  on  6  x  12- 
in.  wall  plates,  supported  by  6x6-in.  posts  setting  close 
against  the  finished  wall.  The  ends  of  the  ribs  were  held  from 


|       Enot5ill  of  Car 


Fig.    142.—  Sketch    Showing    Device    for    Removing    Centering    Ribs,    Burton 

Tunnel. 

closing  in  by  6  x  6-in.  walings,  one  on  each  side,  lag-bolted 
through  the  lining  to  the  timbering.  The  centering  required 
about  315  ft.  B.  M.  of  lumber  per  lineal  foot  of  center.  The 
method  of  removing  the  centers  was  novel.  A  flat  car  had 
erected  on  it  a  narrow  working  platform  high  enough  to  reach 
well  up  into  the  arch.  Along  this  platform  at  the  center  was 
erected  a  sort  of  "horse,"  which  could  be  elevated  and  lowered 
by  jacks.  The  sketch,  Fig.  142,  shows-  the  arrangement.  At 
each  end  and  at  the  middle  of  the  platform  two  guide  posts  a  a 
were  erected  and  braced  upright.  Between  these  guide  posts 
set  plunger  posts  which  were  raised  and  lowered  by  screw 
jacks.  The  three  plunger  posts  carried  a  longitudinal  timber 


TUNNELS    AND    SUBWAYS.  353 

c.  The  car  was  run  under  the  ribs  of  centering  to  be  removed 
and  the  timber  c  raised  by  working  the  jacks  until  it  came  to 
close  bearing  under  the  ribs  d.  The  railings  and  the  wedges 
at  the  foot  of  the  ribs  were  then  removed,  leaving  the  ribs 
hanging  on  the  timber  c.  This  timber  was  then  jacked  down 
to  clear  the  lining  and  the  ribs  rotated  horizontally  on  the 
point  of  suspension  as  a  pivot  until  their  ends  swung  in  over 
the  platform.  The  car  was  then  moved  ahead  to  where  the 
centers  were  to  be  used  again ;  the  ribs  were  rotated  back  to 
their  normal  position  across  tunnel;  the  timber  c  was  jacked 
up,  and  the  wedges  and  railings  placed  at  the  first  of  the  ribs. 

The  concreting  on  the  roof  arch  was  begun  at  the  portal. 
Two  shifts  were  worked  and  42  ft.  of  arch  were  concreted  each 
.shift. 

METHOD  AND  COST  OF  LINING  GUNNISON  TUN- 
NEL.— The  costs  are  for  concrete  in  place  in  the  side  walls 
and  the  arch  of  the  tunnel,  for  a  length  of  440  lin.  ft.  The 
quantity  of  concrete  considered  in  estimating  the  cost  per 
cubic  yard  was  616  cu.  yds.  The  material  was  mixed  and 
placed  in  V2  cu.  yd.  batches,  the  proportion  of  the  mixtures 
being  1-2.2-4.4.  The  final  cost  includes  the  labor  of  excavating 
and  screening  gravel  and  sand,  the  hauling  of  the  same  from 
the  bins  at  the  pit  to  the  storage  bins  at  the  main  shaft,  the 
care  of  the  chutes  in  the  shaft  and  the  mixing  of  the  concrete 
in  the  tunnel  at  the  bottom  of  the  shaft,  the  transportation  of 
the  concrete  from  the  mixer  to  the  traveler,  the  deposition  of 
the  concrete,  the  setting  up  and  taking  down  of  forms  and  the 
cost  of  the  cement.  It  does  not  include  the  construction  of 
the  gravel  pit  chutes  that  hold  the  screens,  the  building  of  the 
road  from  the  gravel  pit  to  the  storage  bins  at  the  shaft,  the 
concree  mixer  and  its  installation,  the  traveler  and  its  installa- 
tion, the  cost  of  material  and  labor  in  the  construction  of  the 
concrete  forms,  the  requisite  power  to  run  the  machinery  and 
other  expenses  of  a  similar  nature. 

The  gravel  used  for  the  concrete  was  obtained  from  a  pit 
situated  on  top  of  a  hill  not  far  from  the  main  shaft  leading 
down  to  the  tunnel.  This  gravel  bed  contains  very  closely  the 
proper  proportions  of  sand  and  gravel  for  the  concrete  aggre- 
ga'-?s.  The  gravel  was  excavated  and  loaded  by  hand  into 
side  dump  cars  of  35  cu.  ft.  capacity.  These  cars  were  run  to 


354 


CONCRETE    CONSTRUCTION. 


the  edge  of  the  hill  where  the  gravel  was  dumped  upon  a 
screen  from  which  it  ran  by  gravity,  passing  thence  into  stor- 
age bins.  From  the  storage  bins  the  sand  and  gravel  were 
drawn  off  into  dump  wagons  having  a  capacity  of  2  cu.  yds. 
and  hauled  a  distance  of  one-half  mile  to  a  second  set  of  stor- 
age bins  located  at  the  top  of  the  shaft  leading  into  the  tun- 
nel. The  road  from  the  storage  bins  at  the  gravel  pit  to  the 
storage  bins  at  the  head  of  the  shaft  was  down  grade.  A  two- 
horse  team  could  readily  haul  2  cu.  yds.  of  gravel  over  this 
road.  The  storage  bins  at  the  top  of  the  shaft  leading  into  the 
tunnel  communicated  with  the  measuring  boxes  at  the  bottom 
of  the  shaft  by  means  of  chutes.  The  measuring  boxes  dis- 
charged directly  into  tram  cars.  The  average  length  of  haul 
from  the  mixer  to  the  place  of  deposition  of  concrete  was 
about  4,500  ft. 

The  concrete  was  placed  in  the  side  walls  by  means  of  a 
traveler,  which  was  so  operated  in  the  tunnel  as  to  allow  the 
passage  of  the  concrete  trains  beneath  it.  The  traveler  was 
64  ft.  long  and  was  provided  with  a  slow  motion  electric  hoist, 
by  which  the  cars  containing  the  concrete  were  elevated  to  the 
top  of  the  traveler  and  thence  transferred  to  any  desired  posi- 
tion. The  concrete  was  dumped  from  these  cars,  into  boxes 
where  any  remixing  or  tempering  that  was  required  was  done, 
after  which  the  concrete  was  shoveled  directly  into  the  forms. 
The  entire  operation  of  handling  the  materials  of  the  concrete, 
it  will  be  seen,  utilized  gravity  to  the  greatest  possible  degree. 

In  order  to  get  a  good  average  cost  per  cubic  yard  for  han- 
dling gravel  and  sand,  this  analysis  has  been  based  on  five 
months'  operation,  from  November,  1906,  to  March,  1907.  In 
these  five  months  there  were  4,123  cu.  yds.  of  sand  and  gravel 
handled.  The  concrete  considered  was  placed  during  the 
month  of  March.  Below  is  given  the  distribution  of  the  cost 
of  the  concrete  as  to  the  specified  divisions  of  the  work  and  as 
to  the  class  of  work  involved  in  each  division.  Measurements 
taken  at  the  mixer  show  that  each  cubic  yard  of  concrete  con- 
tained 0.74  cu.  yds.  of  gravel,  0.445  cu-  yds.  of  sand  and  5.6 
sacks 'of  Portland  cement.  The  total  of  the  aggregates  is, 
therefore,  1.185  cu.  yds.  per  cubic  yard  of  concrete.  The  ce- 
ment costs  $0.62  per  sack  on  the  work,  making  a  cost  of  $3.472 
per  cubic  yard  of  concrete. 


TUNNELS    AND    SUBWAYS.  355 

Excavating  and  screening  4,123  cu.  yds.  gravel — 

Total        Per  cu.  yd. 

cost.  gravel. 

Foreman  66%  days  at  $3.04 $    203.30  $0.049 

Labor,  397^  days  at  $2.56 1,017.60  0.247 

Labor,  116^4  days  at  $2.08 241.80  0.059 


Total   $1,462.70  $0.355 

Hauling  4,123  cu.  yds.  gravel  and  sand — 
2-horse  team  and  driver,  210     days  at 

$3-60    $756.00  $0.183 

2-horse  team  and  driver,  4}^  days  at  $4.        18.00  0.005 


Total   $774.oo  $0.188 

As  there  were  1.185  cu-  yds.  of  gravel  per  cubic  yard  of  con- 
crete the  cost  of  gravel  per  cubic  yard  of  concrete  was  for — 

Excavating  and  screening   (1.185  X  $0.355) $0.421 

Hauling  (1.185  X  $0.188)    0.223 

Total $0.644 

Adding  to  this  the  cost  of  cement  $0.62  X  5-6  =  $3472,  we 
have  $0.644 -f- $3472  =  $4.116,  as  the  cost  of  concrete  mate- 
rials per  cubic  yard  of  concrete.  The  cost  of  labor,  mixing 
and  placing  was  as  follows  for  616  cu.  yds. : 

Total        Per  cu.  yd. 

Mixing  616  cu.  yds.  concrete —  cost.  concrete. 

Superintendent,  2  days  at  $5.83 1 $  11.67  $0.020 

Foreman,   i   day  at  $4.50 4.50  0.007 

Labor,  45  days  at  $3.04 130.72  0.215 

Labor,  93  days  at  $2.56 238.08  0.381 

Hoist  engineer,  34  days  at  $3.52 119.68  0.196 


Total    $504.65  $0.819 

Transporting  616  cu.  yds.  concrete — 

Superintendent,  I  day  at  $5.83^ $     5.83  $0.009 

Foreman,  i  day  at  $4.50 4.50  0.007 

Motorman,  34  days  at  $3.04 103.36  0.175 

Brakeman,  34  days  at  $2.56 87.04  0.135 


Total    , $200.73  $0.326 


356  CONCRETE    CONSTRUCTION, 

Depositing  616  cu.  yds.  concrete — 

Superintendent,  4  days  at  $5.83^ $  23.33  $0.038 

Foreman,  4  days  at  $4.50 18.00  0.029 

Foreman,  68  days  at  $3.04 200.72  0.326 

Labor,  238^  days  at  $2.56 610.56  0.991 


Total $852.61  $1.384 

Setting  and  moving  forms — 

Superintendent,  2  days  at  $5.83-^- $  11.67  $0.018 

Foreman,  2  days  at  $4.50 9.00  0.014 

Carpenter  foreman,  10  days  at  $5 50.00  .     0.080 

Carpenter,  13  days  at  $3.20 41.60  0.067 

Labor,  49  days  at  $3.04 148.96  0.241 

Labor,  19  days  at  $2.56 48.64  0.078 


Total    $309.87  $0.498 

Summarizing  we  have  the  following  cost : 

Materials — 

Cement,  5.6  bags  at  $0.62 $3472 

Gravel   (excavating  and  screening) 0421 

Hauling  gravel  and  sand 0.223 

Total,    materials • $4.116 

Labor — 

Mixing  concrete $0.819 

Transporting  concrete   0.326 

Depositing  concrete    1-394 

Setting  and  moving  forms 0.498 


Total,   labor $3.037 

Grand   total $7. 1 53 

COST  OF  CONCRETE  WORK  IN  LINING  NEW 
YORK  RAPID  TRANSIT  SUBWAY.— The  costs  given  here 
refer  alone  to  the  concrete  work  in  constructing  the  jack  arch 
and  steel  beam  lining  of  the  original  standard  subway.  Figure 
143  shows  the  character  of  this  construction.  Arch  panel 
forms  were  set  up  between  the  wall  beams  and  hung  from  the 
floor  beams  and  filled  behind  and  above  with  1-2-4  trap  rock 
concrete.  The  form  panels  were  used  over  and  over  and  the 


TUNNELS    AND    SUBWAYS. 


357 


concrete  was  machine  mixed.  Common  labor  was  paid  $1.50 
per  8-hour  day;  foremen,  $3;  carpenters,  $3;  enginemen,  $3.50, 
and  masons,  $4.  The  costs  cover  three  sections  and  are  in 
each  case  the  averages  for  the  whole  section.  They  are,  we 
believe,  the  only  itemized  costs  that  have  been  published  for 
concrete  work  on  this  road. 

Two-Track  Subway. — In  this  section  of  two-track  subway 
there  were  8,827  cu.  yds.  of  foundation  concrete  and  6,664  cu- 
yds.  of  concrete  in  wall  and  roof  arches.  The  two  classes  of 
work  cost  as  follows : 


Water  Proofing- 


X2**%$£"  "A-SStfesSSfr 

8$%%&fr.' 


...S'0'- 


i  Depth  of  Concrete  8 
Half   Cross  Section. 


waterproofing-- 

Part  Longitudinal  Section. 

I2'6" x 1Z'6" 

Fig.    143.— Cross-Section    of    New   York    Rapid    Transit    Subway. 


Foundations — 


Total.     Per  cu.  yd. 


Labor  mixing $  4,669 

Labor  placing 5,142 

Materials  and  plant  211 

Cement,  sand,  stone,  etc 30,719 


Total    $40,741 

Roof  and  side  walls — 

Labor  mixing   $  5,444 

Labor  placing   5,623 

Labor  setting  forms J4,746 

Labor  plastering  arches   431 

Materials  and  plant 1,176 

Cement,  sand,  stone,  etc. 23,888 


$0.53 
0.58 

0.02 
348 

$4.6l 


Total 


$7.69 


358 


CONCRETE    CONSTRUCTION. 


Averaging  the  work  we  have  15,491  cu.  yds.  of  concrete 
placed  at  a  cost  of  $5.94  per  cu.  yd. 

Four-Track  Snbivay. — On  two  sections  of  four-track  sub- 
way the  labor  cost  of  mixing  and  placing  concrete  similarly 
divided  was  as  follows : 

Section  A.      Section  B. 

Foundations —  Per  cu.  yd.     Per  cu.  yd. 

Labor  mixing   $0.97  $0.94 

Labor  placing 0.96  0.95 

Power    0.14  0.16 


Total    $2.07 

Roof  and  side  walls — 

Labor  mixing   $0.79 

Labor  placing  0.85 

Labor  setting  forms 2.01 

Labor  plastering  arches   0.16 

Power    0.28 

Total    $4.09 


$2.05 


$343 


Part     Side     Elevation. 


Half       Cross        Section. 


Fig.   144.— Traveling  Form   for   Side  Walls,   New   York   Subway  Tunnels. 

TRAVELING  FORMS  FOR  LINING  NEW  YORK 
RAPID  TRANSIT  RY.  TUNNELS.— In  constructing  the 
tunnels  under  Park  Ave.  and  under  the  north  end  of  Central 
Park  for  the  New  York  Rapid  Transit  Ry.,  traveling  centers 
and  side  wall  forms  were  used  for  the  concrete  lining.  The 
mixing  plants  were  installed  in  the  shafts  and  consisted  gen- 
erally of  gravity  mixers  charged  at  the  surface  and  discharg- 
ing into  skip  cars  running  on  the  tunnel  floor. 

The  forms  used  in  the  Park  Ave.  tunnel  are  shown  by  Figs. 
144  and  145 ;  those  used  in  the  Central  Park  tunnel  differed 
only  in  details.  The-  method  of  work  was  slightly  different 


TUNNELS    AND    SUBWAYS. 


359 


in  the  two  tunnels,  but  was  substantially  as  follows:  Three 
platforms  mounted  on  wheels  were  used  in  each  set  and  two 
sets  were  employed.  Ahead  came  a  traveler  carrying  the  side 
wall  forms,  next  came  a  shorter  traveler  carrying  a  derrick, 
and  last  came  the  traveler  carrying  the  roof  centers.  The  ar- 


I  tleva-non. 

Fig.    145.— Traveling  Form   for   Roof  Arch,   New  York   Subway  Tunnels. 

rangement  as  operated  in  the  Central  Park  tunnel  is  shown  by 
Fig.  146.  In  the  Park  Ave.  tunnel  the  "bridges"  w~re  dis- 
pensed with,  the  skips  being  hoisted  through  the  open  end 
bays  of  the  derrick  car  and  set  directly  on  the  cars  on  the 
center  traveler. 


-j  

\Bridck 

69T  7AJ5XC/ry 

Side  Wai/ 
PJoitform 

Lterrick 
r    _^ 

E 

y^/r/7  P/afform 

ror/71 

SE3& 

>    ^ar  TratcK-^ 

/ 

i 

l          i 

/,x»w  v«  v-v*  W/N"  7' 

•r//  */«   y/\y/'\y/i\y/^///^ 

Fig.    146. — Sketch    Plan    of   Traveling    Forms,    New    York    Subway    Tunnels. 

The  traveler  carrying  the  side  wall  forms  was  set  in  posi- 
tion and  blocked,  the  grade  and  line  being  given  by  the  track 
rails,  which  had  been  set  exactly  for  that  purpose.  The  side 
wall  forms  differed  slightly  in  the  two  tunnels ;  those  for  the 
Park  Ave.  tunnel  shown  by  Fig.  144  formed  the  vertical  por- 


CONCRETE    CONSTRUCTION. 


tion  of  the  wall  only  so  that  when  the  arch  forms,  Fig.  145, 
followed  a  space  A  B  was  left  which  had  to  be  molded  by 
separate  sector-like  forms.  The  side  wall  forms  for  the  Cen- 
tral Park  work  were  constructed  as  shown  by  Fig.  147,  being 
curved  at  the  top  to  merge  into  the  arch  centers.  In  the  Park 
Ave.  work  the  wall  studs  were  adjusted  in  or  out  by  means  of 
wedges  and  slotted  bolt  holes.  In  the  Central  Park  work  the 
studs  A  Fig.  145  were  hung  by  ^-in.  bolts  from  the  pieces  B 
spiked  to  line  onto  the  cross-braces.  The  bottom  was  then 
lined  up  by  means  of  wedges  at  D.  The  side  wall  studs  being 
lined  up,  the  bottom  lagging  boards  were  placed  and  filled 
behind  by  shoveling  the  concrete  into  them  direct  from  skip 
cars  on  the  adjacent  tracks  on  the  tunnel  floor.  In  this  way 
the  side  walls  were  built  up  to  the  tops  of  the  forms. 


Fig.    147.— Sketch    Showing  Detail   of   Side   Wall   Forms,    New   York   Subway 

Tunnels. 

As  soon  as  the  side  wall  concrete  had  set  the  forms  were 
struck  and  the  traveler  was  moved  ahead  and  set  for  another 
section  of  wall.  The  derrick  and  roof  arch  travelers  were 
then  moved  into  position  between  the  finished  walls,  and  the 
arch  traveler  was  jacked  up  and  aligned.  Skip  cars  coming 
from  the  mixer  were  run  under  the  derrick  traveler,  where  the 
skips  were  lifted  by  the  derrick  and  set  on  the  platform  cars 
to  be  run  alongside  the  work.  The  arch  lagging  was  placed 
a  piece  at  a  time  and  filled  behind  by  shoveling  direct  from 
the  skips.  As  the  crown  was  approached  the  lagging  was 
placed  in  short  lengths  and  filled  in  over  the  ends,  the  con- 
crete being  shoveled  in  two  lifts;  in  Fig.  145  the  line  C  D  indi- 


TUNNELS    AND    SUBWAYS.  361 

cates  the  position  of  the  shoveling  board.  The  centers  were 
struck  by  lowering  the  jack  supported  traveler  down  onto  the 
track  rails. 

COST  OF  MIXING  AND  PLACING  SUBWAY  LIN- 
ING, LONG  ISLAND  R.  R.,  BROOKLYN,  N.  Y.— The  sub- 
way carrying  the  two  tracks  of  the  Long  Island  R.  R.  under 
Atlantic  Ave.,  in  Brooklyn,  New  York  city,  has  a  lining  con- 
sisting of  an  invert  arch  12  ins.  thick  at  the  center,  side  walls 
4y2  ft.  thick  at  the  base  and  3  ft.  thick  at  the  top,  and  a  roof 
of  jack  arches  between  steel  I-beams  5  ft.  apart.  The  dimen- 
sions inside  the  concrete  are  16  x  20  ft.  A  1-8  mixture  of  ce- 
ment, sand,  gravel  and  stone  was  used  in  the  floor  and  walls 
and  a  1-6  mixture  of  the  same  materials  in  the  jack  arches. 
A  bag  of  cement  was  called  I  cu.  ft.,  so  that  a  barrel  was  4 
cu.  ft.  A  Hains  gravity  mixer  and  a  batch  mixer  were  used 
and  careful  records  were  kept  of  all  quantities. 

General  Data. — During  1903,  about  13,880  cu.  yds.  of  the  1-8 
concrete  were  placed,  90  per  cent,  of  which  was  mixed  in  the 
gravity  mixer  and  10  per  cent,  in  the  batch  mixer.  Of  the  1-6 
concrete  5,320  cu.  yds.  were  placed,  85  per  cent,  of  which  was 
mixed  in  the  gravity  mixer  and  15  per  cent,  in  the  batch 
mixer. 

Gravity  Mixer  Work. — During  1903,  there  were  16,940  cu. 
yds.  of  concrete  mixed  in  gravity  mixers,  requiring  2,860  days' 
labor  mixing  and  4,000  days'  labor  placing.  Wages  were  $1.50 
a  day  and  the  cost  was  26  cts.  per  cu.  yd.  for  mixing  and  33 
cts.  for  placing,  making  a  total  of  59  cts.  per  cu.  yd.  During 
the  month  of  August  when  2,800  cu.  yds.  were  mixed  the  cost 
was  as  low  as  24  cts.  for  mixing,  plus  22  cts.  for  placing,  or  a 
total  of  46  cts.  per  cu.  yd.  for  mixing  and  placing.  The  mixer 
averaged  about  113  cu.  yds.  per  day  with  a  gang  of  19  men 
mixing  and  26  men  placing.  The  average  size  of  batch  was 
0.46  cu.  yd.  In  1904,  20,000  cu.  yds.  were  mixed  in  190  days, 
worked  with  a  gang  of  19  men  mixing ;  the  gang  placing  con- 
sisted of  25  men.  The  cost  was  as  follows: 

Item.  Total.        Per  cu.  yd. 

2,950  days  labor  mixing $  4,870  24  cts. 

4,760  days  labor  placing 7,300  36  cts. 


Total    $12,170  -      60  cts. 


362  CONCRETE    CONSTRUCTION. 

During  the  best  month  of  1904,  the  labor  cost  was  16  cts. 
for  mixing  and  29  cts.  for  placing,  or  a  total  of  45  cts.  per 
cu.  yd. 

Batch  Mixer  Work. — During  1903  the  batch  mixer  mixed 
2,390  cu.  yds.  in  970  labor  days  mixing  and  740  labor  days 
placing  at  a  cost  of  59  cts.  per  cu.  yd.  for  mixing  and  55  cts. 
per  cu.  yd.  for  placing,  or  a  total  of  $1.04  per  cu.  yd.  During 
the  month  of  June  the  cost  was  as  low  as  40  cts.  for  mixing 
and  30  cts.  for  placing,  or  70  cts.  per  cu.  yd.  for  mixing  and 
placing.  The  wages  paid  were  $1.50  per  day  and  the  average 
gangs  were  n  men  mixing  and  14  men  placing;  the  average 
batch  mixed  was  0.57  cu.  yd.  and  the  average  output  was  35 
cu.  yds.  per  day.  During  1904,  the  mixer  worked  153  days  and 
averaged  46  cu.  yds.  per  day ;  the  average  size  of  batch  was 
0.44  cu.  yd.  The  average  gangs  were  13  men  mixing  and  n 
men  placing.  The  labor  cost  of  7,000  cu.  yds.  was  as  follows : 

Item.  Total.  Per  cu.  yd. 

1,910  days  labor  mixing $3^75  45  cts. 

1,740  days  labor  placing. 2,660  38  cts. 


Total    $5,835  83  etc. 

Haulage. — The  costs  given  comprise  in  mixing,  the  cost  of 
delivering  the  materials  to  the  mixer,  and,  in  placing,  the  cost 
of  hauling  the  concrete  away.  A  Robins  belt  conveyor  was 
used  to  deliver  materials  to  the  gravity  mixer  and  this  ac- 
counts, in  a  large  measure,  for  the  lower  cost  of  mixing  by 
gravity.  The  mixed  concrete  was  hauled  from  both  mixers 
in  dump  cars  pushed  by  men. 

Form  Work. — The  labor  cost  of  forms  for  19,300  cu.  yds.  of 
concrete  placed  in  1903  was  $16,800,  or  87  cts.  per  cu.  yd.  of 
concrete.  The  total  labor  days  consumed  on  form  work  was 
6,340  at  $2.70  per  day.  The  total  cost  of  concrete  in  place  for 
mixing,  placing  and  form  work  was  $1.46  per  cu.  yd.,  not  in- 
cluding lumber  in  forms,  fuel,  interest  and  depreciation. 


CHAPTER   XVII. 

METHODS   AND    COST   OF   CONSTRUCTING   ARCH 
AND   GIRDER  BRIDGES. 

The  construction  problems  in  arch  and  girder  bridges  of 
moderate  spans  are  simple,  and  with  the  exception  of  center 
construction  and  arrangement  of  plant  for  making  and  placing 
Concrete,  are  best  explained  by  citing  specific  examples  of 
bridge  work.  This  is  the  arrangement  followed  in  this  chap- 
ter. 

CENTERS. — The  construction  of  centers  is  no  less  im- 
portant a  task  for  concrete  arches  than  for  stone  arches.  This 
means  that  success  in  the  construction  of  concrete  arches  de- 
pends quite  as  much  upon  the  sufficiency  of  the  center  con- 
struction as  it  does  upon  any  other  portion  of  the  work.  The 
center  must,  in  a  word,  remain  as  nearly  as  possible  invariable 
in  level  and  form  from  the  time  it  is  made  ready  for  the  con- 
crete until  the  time  it  is  removed  from  underneath  the  arch, 
and,  when  the  time  for  removal  comes,  the  construction  must 
be  such  that  that  operation  can  be  performed  with  ease  and 
without  shock  or  jar  to  the  masonry.  The  problem  of  center 
construction  is  thus  the  two-fold  one  of  building  a  structure 
which  is  immovable  until  movement  is  desired  and  then  moves 
at  will.  Incidentally  these  requisites  must  be  obtained  with 
the  least  combined  expenditure  for  materials,  framing,  erec- 
tion and  removal,  and  with  the  greatest  salvage  of  useful 
material  when  the  work  is  over.  The  factors  to  be  taken 
count  of  are  it,  will  be  seen,  numerous  and  may  exist  in  in- 
numerable combinations. 

Centers  may  be  classified  into  two  types:  (i)  Centers 
whose  supports  must  be  arranged  so  as  to  leave  a  clear  open- 
ing under  the  center  for  passing  craft  or  other  purposes,  and 
(2)  centers  whose  supports  can  be  arranged  in  any  way  that 
judgment  and  economy  dictate.  Centers  of  the  first  class  are 
commonly  called  cocket  centers.  As  examples  of  a  cocket  and 

363 


364 


CONCRETE    CONSTRUCTION. 


of  a  supported  center  and  also  as  examples  of  well  thought  out 
center  design  we  give  the  two  centers  shown  by  Figs.  148  and 
149,  both  designed  for  a  5O-ft.  span  segmental  arch  by  the 
same  engineer.  The  development  of  the  center  shown  by 


Longitudinal  See+lor*. 

Fig.  148.— Center  for  50  ft.   Arch   Span   (Supported). 

Fig.  148  into  the  cocket  center  shown  by  Fig.  149  is  plainly 
traceable  from  the  drawings.  In  respect  to  the  center  shown 
by  Fig.  149  which  was  the  construction  actually  adopted  we 
are  informed  that  16,464  ft.  B.  M.  were  required  for  a  center 


Fig.   149.— Center  for  50-ft.  Arch   Span  (Cocket). 

36  ft.  long,  that  the  framing  cost  about  $12  per  M.  ft.  B.  M., 
with  carpenters'  wages  at  $4  per  day,  and  that  the  cost  of 
bolts  and  nuts  was  about  $1.50  per  M.  ft.  B.  M.  With  lumber 
at  $20  per  M.  ft.  B.  M.,  this  center  framed  and  erected  would 


ARCH  AND   GIRDER   BRIDGES.  365 

cost  about  $35  per  M.  ft.  B.  M.  As  an  example  of  framed 
centers  for  larger  spans  we  show  by  Fig.  158  the  centers  for 
the  Connecticut  Avenue  Bridge  at  Washington,  D.  C,  with 
costs  and  quantities ;  other  references  to  costs  are  contained 
in  the  index. 

A  center  of  very  economical  construction  is  shown  by  Fig. 
159,  and  is  described  in  detail  in  the  accompanying  text.  The 
distinctive  feature  of  this  center  is  the  use  of  lagging  laid 
lengthwise  of  the  arch  and  bent  to  curve.  Another  example 
of  this  form  of  construction  may  be  found  in  a  3-span  arch 
bridge  built  at  Mechanicsville,  N.  Y.,  in  1903.  The  viaduct 
was  17  ft.  wide  over  all,  and  consisted  of  two  loo-ft.  spans 
and  one  5o-ft.  span.  Pile  bents  were  driven  to  bed  rock,  the 
piles  being  spaced  6  ft.  apart  and  the  bents  10  ft.  apart.  Each 
bent  was  capped  with  rox  12-in.  timber.  On  these  caps  were 
laid  four  lines  of  lox  12-in.  stringers,  and  8x  zo-in.  posts  3  ft. 
apart  were  erected  on  these  stringers,  and  each  set  of  four 
posts  across  the  arch  was  capped  with  8  x  lo-in  timbers  the 
ends  of  which  projected  3  ft.  beyond  the  faces  of  the  arch. 
The  tops  of  these  cross  caps  were  beveled  to  receive  the  lag- 
ging which  was  put  on  parallel  with  the  center  line  of  the  via- 
duct, sprung  down  and  nailed  to  the  caps.  This  lagging  con- 
sisted of  rough  i-in.  boards  for  a  lower  course,  on  top  of 
which  was  laid  i-in.  boards  dressed  on  the  upper  sides.  Hard- 
wood wedges  were  used  under  the  posts  for  removing  the  cen- 
ters. In  the  centers,  forms  and  braces  for  the  three  arches 
there  were  used  140,000  ft.  B.  M.  of  lumber.  The  structure 
contained  2,500  cu.  yds.  of  concrete. 

Another  type  of  center  that  merits  consideration  in  many 
places  is  one  developed  by  Mr.  Daniel  B.  Luten  and  used  by 
him  in  the  construction  of  many  arches  of  the. Luten  type  of 
reinforced  concrete  arch.  The  particular  feature  of  this  type 
of  arch  is  that  in  shallow  streams  for  bridges  of  ordinary  span 
the  ends  of  the  arch  ring  are  tied  together  across  stream  by  a 
slab  of  concrete  reinforced  to  take  tension.  This  slab  is  in- 
tended to  serve  the  double  purpose  of  a  tie  to  keep  the  arch 
from  spreading  and  thus  reduce  the  weight  of  abutments  and 
of  a  pavement  preventing  scour  and  its  tendency  to  under- 
mine the  abutments.  Incidentally  this  concrete  slab,  which  is 


366  CONCRETE    CONSTRUCTION. 

built  first,  serves  as  a  footing  for  the  supports  carrying  the 
arch  center. 

As  an  illustration  of  the  center  we  choose  a  specific  struc- 
ture. In  building  a  95-ft.  span,  n-ft.  i-in.  rise  arch  bridge  at 
Yorktown,  Ind.,  in  1905,  the  centers  were  designed  so  as  to 
avoid  the  use  of  sand  boxes  or  wedges.  Ribs  of  2xi2-in. 
pieces  cut  to  t-he  arc  of  the  arch  soffit  were  supported  on 
uprights  standing  on  the  concrete  stream  bed  pavement.  The 
uprights  were  so  proportioned  by  Gordon's  formula  for  col- 
umns that  without  bracing  they  would  be  too  light  to  support 
the  load  of  concrete  and  earth  filling  that  was  to  come  upon 
them,  but  when  braced  at  two  points  dividing  the  uprights 
approximately  into  thirds  they  would  support  their  loading 
rigidly  and  without  buckling.  The  design  in  detail  was  as 
follows :  The  uprights  near  the  middle  of  the  span  were  about 
15  ft.  long  and  were  spaced  7  ft.  apart  across  the  stream  and 
3  ft.  apart  across  the  bridge.  Each  upright  then  was  to  sup- 
port a  loading  of  concrete  of  7  ft.  x  3  ft.  x  26  ins.  and  an  earth 
fill  i  ft.  x  7  ft.  x  3  ft.,  or  a  total  load  of  about  9,000  Ibs.  Apply- 
ing Gordon's  formula  for  struts  with  free  ends, 

fS 

p  — 


125  /i2 

where  P  is  the  total  load  =  9,000  Ibs.,  /  is  fibre  stress  for  oak 
=  i, 600  Ibs.,  /  is  length  of  strut  in  inches  and  h  is  least  diam- 
eter of  strut  in  inches,  it  was  found  that  for  a  length  of  15  ft. 
a  7x7-in.  upright  would  be  required  to  satisfy  the  formula, 
but  for  a  length  of  5  ft.,  which  would  result  from  bracing  each 
strut  at  two  points,  a  4x4-in.  timber  satisfied  the  formula. 
Therefore,  4  x  4-in.  timbers  braced  at  two  points  were  used  for 
the  longest  uprights.  About  30  days  after  the  completion  of 
the  arch  the  bracing  was  removed  from  the  uprights,  begin- 
ning at  the  ends  of  the  span  and  working  towards  the  middle. 
As  the  bracing  was  being  removed  the  uprights  gradually 
yielded,  buckling  from  4  to  6  ins,  from  the  vertical  and  allow- 
ing the  arch  to  settle  about  y\  in.  at  the  crown.  This  type  of 
center  has  been  successfully  employed  in  a  large  number  of 
bridges. 


ARCH   AND    GIRDER    BRIDGES. 


367 


Figure  150  shows  a  center  for  a  125-ft.  span  parabolic  arch 
with  the -amount  and  character  of  the  stresses  indicated  and 
with  a  diagram  of  the  actual  deflections  as  measured  during 
the  work. 


Friction  of  Concrete  not  Considered  except  apper 
Blocks  No.7,4arKtl  which  we're  regarded  as  he/rr 
from  Sliding  by  Friction. 

/til  Stress  Figures  nor  otherwise 
Noted,  Indicate  Actual  Stress  in  founds. 


fg 

i*£j 


Fig    150.— Center   for  125-ft.    Span    Parabolic   Arch  with  Diagram   of 
Deflections. 

In  calculating  centers  of  moderate  span  there  is  seldom  need 
of  more  than  the  simple  formulas  and  tables  given  in  Chapter 
IX.  When  the  spans  become  larger,  and  particularly  when 
they  become  very  large — over  200  ft. — the  problem  of  calculat- 


368 


CONCRETE    CONSTRUCTION. 


ing  centers  becomes  complex.  None  but  an  engineer  familiar 
with  statics  and  the  strengths  of  materials  and  knowing  the 
efficiency  of  structural  details  should  be  considered  for  such 
a  task.  Such  computations  are  not  within  the  intended  scope 
of  this  book,  and  the  design  of  large  centers,  will  be  passed 
with  the  presentation  of  a  single  example,  the  center  for  the 
Walnut  Lane  Bridge  at  Philadelphia,  Pa. 

The  main  arch  span  of  the  Walnut  Lane  Bridge  consists 
of  twin  arches  spaced  some  16  ft.  apart  at  the  crowns  and 
connected  across  by  the  floor.  Each  of  the  twin  arch  rings  has 
a  span  of  232  ft.  and  a  rise  of  70^4  ft.,  is  9^2  ft.  thick  and  21^ 
ft.  wide  at  the  skew-back  and  5^/2  ft.  thick  and  18  ft.  wide  at 
the  crown.  The  plan  was  to  build  a  center  complete  for  one 


'  IZ'O'hng.bwItin 
Cross  Section 

Fig.   151. — Center  for 


Elevation. 
5-ft.   Span  Arch  at  Philadelphia,   Pa. 


arch  ring  and  then  to  shift  it  along  and  re-use  it  for  building 
the  other  arch  ring.  The  centering  used  is  shown  in  diagram 
by  Fig.  151.  It  consists  of  five  parts:  (i)  Six  concrete 
piers  running  the  full  width  of  the  bridge  upon  which  the 
structure  was  moved;  (2)  a  steel  framework  up  to  E  G,  called 
the  "primary  bent";  (3)  a  separate  timber  portion  below  the 
heavy  lines  E  I  and  W  I' ;  (4)  the  "main  staging"  included  in 
the  trapezoid  E  I  W  /',  and  (5)  the  "upper  trestle"  extending 
from  /  /'  to  the  intrados. 

The  primary  bent  consists  of  four  I-beam  post  bents  having 
channel  chords,  the  whole  braced  together  rigidly  by  angles. 
Each  bent  is  carried  on  \y2  ft.  x  6  in.  steel  rollers  running  on 
a  track  of  19  x  y2  in.  plate  on  top  of  the  concrete  piers.  Be- 


ARCH  AND   GIRDER   BRIDGES.  369 

tween  the  primary  bents  and  the  main  staging,  and  also 
between  the  main  staging  and  the  upper  trestles  are  lifting 
devices.  The  mode  of  operation  planned  is  as  follows :  When 
the  center  has  been  erected  as  shown  and  the  arch  ring  con- 
creted the  separate  stagings  under  K  I  and  K'  I'  are  taken 
down.  Next  the  portions  under  the  lines  /  E  and  /'  W  will  be 
taken  down  and  erected  under  the  second  arch.  Finally  the 
remainder  of  the  center  will  be  shifted  sidewise  on  the  rollers 
to  position  under  the  second  arch. 

MIXING  AND  TRANSPORTING  CONCRETE.— The 
nature  of  the  plant  for  mixing  and  handling  the  concrete  in 
bridge  work  will  vary  not  only  with  varying  local  conditions 
but  with  the  size  and  length  of  the  bridge.  For  single  span 
structures  of  moderate  size  the  concrete  can  be  handled 
directly  by  derricks  or  on  runways  by  carts  and  wheelbar- 
rows. For  bridges  of  several  spans  the  accepted  methods  .of 
transport  are  cableways,  cars  and  cars  and  derricks.  Typical 
examples  of  each  type  of  plant  are  given  in  the  following 
paragraphs,  and  also  in  the  succeeding  descriptions  of  the 
Connecticut  Avenue  Bridge  at  Washington,  D.  C,  and  of  a 
five-span  arch  bridge. 

Cableway  Plants. — The  bridge  was  710  ft.  long  be- 
tween abutments  and  62  ft.  wide;  it  had  a  center  span  of  no 
ft.,  flanked  on  each  side  by  a  ioo-ft.,  a  QO-ft.  and  an  8o-ft. 
span.  The  mixing  plant  was  located  at  one  end  of  the  bridge 
and  consisted  of  a  Drake  continuous  mixer,  discharging  one- 
half  at  the  mixer  and  one-half  by  belt  conveyor  to  a  point  50 
ft.  away,  so  as  to  supply  the  buckets  of  two  parallel  cable- 
ways.  The  mixer  output  per  lo-hour  day  was  400  cu.  yds. 
and  the  mixing  plant  was  operated  at  a  cost  of  $27  per  day, 
making  the  cost  of  mixing  alone  6^4  cts.  per  cu.  yd.  The  sand 
and  gravel  were  excavated  from  a  pit  4^  miles  away  and  de- 
livered by  electric  cars  to  the  bridge  site  at  a  cost  of  50  cts. 
per  cu.  yd.  Two  93O-ft.  span  Lambert  cableways  set  parallel 
with  the  bridge,  one  25  ft.  each  side  of  the  center  axis,  were 
used  to  deliver  the  concrete  from  mixer  to  forms.  The  cable- 
way  towers  were  70  ft.  high  and  the  cables  had  a  deflection 
of  35  ft. ;  they  were  designed  for  a  load  of  7  tons,  but  the 
average  load  carried  was  only  3  or  4  tons.  These  cableways 
handled  practically  all  the  materials  used  in  the  construction 


370  CONCRETE    CONSTRUCTION. 

of  the  bridge.  They  delivered  from  mixer  to  the  work  400 
cu.  yds.  of  concrete  450  ft.  in  10  hours  at  a  cost  of  2  cts.  per 
cu.  yd.  for  operation. 

Another  example  of  cableway  arrangement  for  concreting 
bridge  piers  is  shown  by  Fig.  I5ia.  The  river  was  about 
800  ft.  wide,  about  3  ft.  deep  and  had  banks  about  20  ft.  high. 
The  piers  were  about  21  ft.  high.  The  towers  for  the  cable- 
way  consisted  of  a  55-ft.  derrick  without  boom,  placed  near 
the  bank  on  the  center  line  of  the  piers  and  well  guyed  and  a 
two-leg  bent  placed  in  the  middle  of  the  river  and  held  in  place 
by  four  cable  guys  anchored  to  the  river  bottom.  A  J^-in. 
steel  hoisting  cable  was  stretched  from  a  deadman  on  shore, 
about  150  ft.  back  of  the  derrick,  and  followed  along  the  center 
line  of  the  piers,  past  the  derrick  just  clearing  it,  to  the  bent  in 
the  middle  of  the  river.  At  the  top  of  this  bent  was  a  i6-in. 
cable  block.  Through  this  block  the  cable  passed  down  and 


k 


Hoish'ng  Engine  Cng.-Contr 

Fig.   151a. — Cableway  for  Concreting  Bridge  Piers. 

was  made  fast  to  a  weight,  consisting  of  a  skip  loaded  with 
concrete  until  the  cable  had  the  required  tension,  and  a  pitch 
of  1 8  to  20  ft.  from  center  of  river  to  anchor  on  shore.  In 
order  to  secure  the  required  pitch  from  the  shore  to  the  river 
bent  the  boom  fall  of  the  derrick  was  hooked  onto  the  cable 
at  the  foot  of  the  mast,  and  then,  by  going  ahead  on  the  single 
drum  hoisting  engine,  was  raised  to  the  mast  head.  This  gave 
the  cable  a  pitch  of  18  to  20  ft.  from  mast  head  to  top  of  bent 
in  river.  The  carriage  used  on  the  cableway  consisted  of  two 
i6-in.  cable  sheaves  with  iron  straps,  forming  a  triangle,  with 
a  chain  hanging  from  the  bottom  point,  to  which  was  attached 
the  5  cu.  ft.  capacity  concrete  bucket.  The  concrete  was 
mixed  on  a  platform  at  the  foot  of  the  mast.  When  ready  for 
operation  the  chain  on  the  carrier  was  hooked  to  the  bucket 
of  concrete,  the  engine  started,  and  both  bucket  and  cable 
raised,  the  former  running  by  gravity  to  the  pier.  The  speed 
of  descent  was  governed  by  the  height  to  which  the  cable  was 


ARCH   AND   GIRDER   BRIDGES. 


371 


raised  on  the  derrick,  and  as  the  bucket  neared  the  dumping 
point  the  engine  was  slacked  off  and  the  cable  leveled.  The 
bucket  was  dumped  by  a  man  on  a  staging  erected  on  the  pier 
form.  For  the  return  of  the  bucket  the  engine  was  slacked 
off  and  the  weight  on  the  river  bent  would  pull  the  cable  tight 
so  that  the  pitch  would  be  toward  the  shore  and  the  bucket 
could  run  down  the  grade  to  the  mixing  platform,  the  speed 
being  governed  as  before  by  leveling  the  cable.  When  the 
piers  were  completed  to  the  middle  of  the  river  the  engine  and 
derrick  were  taken  over  to  opposite  side  of  the  river,  the  bent 
being  left  in  the  middle,  and  the  work  continued.  By  using 
the  extreme  grade  of  the  cable  it  was  found  that  the  bucket 
would  run  from  the  platform  to  the  bent  (400  ft.)  in  less  than 
35  seconds. 

Car  Plant  for  4-Span  Arch  Bridge. — The  bridge  had  four 
no-ft.  skew  spans,  and  a  total  length  of  554  ft.  The  mixing 
plant  was  located  alongside  one  abutment  on  a  side  hill  so  that 


Fig.    152.— Sketch    Showing   Car  and   Trestle   Plant   for   Concreting  an   Arch 

Bridge. 

sand  and  stone  could  be  stored  on  the  slope  above.  The  mixer 
was  set  on  a  platform  high  enough  to  clear  cars  below.  Above 
it  and  to  the  rear  a  charging  platform  reached  back  to  the 
stone  and  sand  piles.  Side  dump  cars  running  on  a  track  on 
the  charging  platform  took  sand  and  stone  to  the  mixer  and 
cement  was  got  from  a  cement  house  at  charging  platform 
level.  The  concrete  for  the  abutment  adjacent  to  the  mixer 
was  handled  in  buckets  by  a  guy  derrick.  A  trestle,  Fig.  152, 
was  then  built  out  from  the  mixer  to  the  first  pier ;  this  trestle 
was  so  located  as  to  clear  the  future  bridge  about  20  ft.  and 
was  carried  out  from  shore  parallel  to  the  bridge  until  nearly 
opposite  the  pier  site,  where  it  was  swung  toward  and  across 
the  pier.  The  concrete  was  received  from  the  mixer  in  bottom 
dump  push  cars  ;  these  cars  were  run  out  over  the  pier  site  and 
dumped.  When  the  first  pier  had  been  concreted  to  springing 
line  level,  the  main  trestle  was  extended  to  opposite  the  second 


372  CONCRETE    CONSTRUCTION. 

pier  and  the  branch  track  was  removed  from  over  the  first  pier 
and  placed  over  the  second  pier.  This  operation  was  repeated 
for  the  third  pier.  The  last  extension  of  the  main  track  was  to 
the  far  shore  abutment,  where  the  bodies  of  the  cars  were 
hoisted  by  derrick  and  dumped  into  the  abutment  forms.  The 
derrick  was  the  same  one  used  for  the  first  abutment  having 
been  moved  and  set  up  during  the  construction  of  the  inter- 
mediate piers.  To  construct  the  arches  a  second  trestle  was 
built  composed  partly  of  new  work  and  partly  of  the  staging 
for  the  arch  centers.  This  trestle  rose  on  an  incline  from  the 
mixer  to  the  first  pier  across  which  it  was  carried  at  approxi- 
mately crown  level  of  the  arch.  The  concrete  for  the  portion 
of  the  pier  above  springing  line  and  for  the  lower  portions  of 
the  haunches  was  dumped  direct  from  the  cars.  For  the  upper 
parts  of  the  arch  the  concrete  was  brought  to  the  pier  track  in 
two-wheel  carts  on  push  cars  and  thence  these  carts  were 
taken  along  the  arch  toward  shore  on  runways.  When  the 
first  arch  had  been  concreted  the  second  trestle  was  extended 
to  pier  two  and  the  operation  repeated  to  concrete  the  second 
arch. 

Hoist  and  Car  Plant  for  21 -Span  Arch  Viaduct. — The  double 
track  concrete  viaduct  replaced  a  single  track  steel  viaduct, 
being  built  around  and  embedding  the  original  steel  structure 
which  was  maintained  in  service.  The  concrete  viaduct  con- 
sisted of  21  spans  of  26  ft.,  7  spans  of  16  ft.,  and  2  spans  of  22 
ft.  With  piers  it  required  about  15,000  cu.  yds.  of  concrete. 
Two  Ransome  concrete  hoists,  one  on  each  side  of  the  original 
steel  structure  near  one  end,  were  supplied  with  concrete  by  a 
No.  4  Ransome  mixer.  The  mixer  discharged  direct  into  the 
bucket  of  one  hoist  and  by  means  of  a  shuttle  car  and  chute 
into  the  bucket  of  the  other  hoist. 

The  shuttle  car  ran  from  the  mixer  up  an  incline  laid  with 
two  tracks,  one  narrow  gage  and  one  wide  gage,  having  the 
same  center  line.  The  car  was  open  at  the  front  end  and  its 
two  rear  wheels  rode  on  the  broad  gage  rails  and  its  two 
forward  wheels  rode  on  the  narrow  gage  rails.  At  the  top 
of  the  incline  the  narrow  gage  rails  pitched  sharply  below  the 
grade  of  the  broad  gage  rails  so  that  the  rear  end  of  the  car 
was  tilted  up  enough  to  pour  the  concrete  into  a  chute  which 


ARCH  AND   GIRDER   BRIDGES.  373 

led  to  the  bucket  of  the  hoist.  The  sand  and  gravel  bins  were 
elevated  above  the  mixer  and  received  their  materials  from 
cars  which  dumped  directly  from  the  steel  viaduct. 

The  hoist  buckets  discharged  into  two  hoppers  mounted  on 
platforms  on  the  old  viaduct.  These  platforms  straddled  two 
narrow  gage  tracks,  one  on  each  side  of  the  old  viaduct  paral- 
lel to  and  clearing  the  main  track.  These  side  tracks  were 
carried  on  the  cantilever  ends  of  long  timbers  laid  across  the 
old  viaduct  between  ties.  At  street  crossings  the  overhanging 
ends  of  the  long  timbers  were  strutted  diagonally  down  to  the 
outside  shelf  of  the  bottom  chords  of  the  plate  girder  spans. 
Six  cars  were  used  and  the  concrete  was  dumped  by  them 
directly  into  the  forms ;  the  fall  from  the  track  above  being  in 
some  cases  40  ft.  The  hoists  and  shuttle  car  were  operated  by 
an  &l/2  x  12-in.  Lambert  derrick  engine,  the  boiler  of  which 
also  supplied  steam  to  the  mixer  engine.  The  concrete  cars 
were  operated  by  cable  haulage  by  two  Lambert  7  x  loin, 
engines. 

The  labor  force  employed  in  mixing  and  placing  concrete, 
including  form  work,  was  45  men,  and  this  force  placed  on  an 
average  200  cu.  yds.  of  concrete  per  day.  Assuming  wages 
we  get  the  following  costs  of  different  parts  of  the  work  for 
labor  above : 

Item.  Per  day.  Per  cu.  yd. 

i  timekeeper  at  $2.50 $    2.50  $0.0125 

i  general  foreman  at  $5 5.00  0.0250 

3  enginemen  at  $5 15.00  0.0750 

i  carpenter  foreman  at  $4 4.00  0.0200 

12  carpenters   at  $3.50 42.00  0.2100 

i  foreman  at  $4 4-OO  0.0200 

8  men    mixing  and    transporting    at 

$175 H-OO 

13  men  placing  concrete  at  $1.75 22.75 

i  foreman  finishing  at  $4 4.00 

4  laborers  finishing  at  $1.75 7.00 

45  men  at  $2.70  $120.25  $0.6012 


374 


CONCRETE    CONSTRUCTION. 


It  is  probable  that  the  carpenter  work  includes  merely  shift- 
ing and  erecting  forms  and  not  the  first  cost  of  framing 
centers.  No  materials,  of  course,  are  included.  It  should  be 
kept  in  mind  that  while  the  output  and  labor  force  are  exact 
the  wages  are  assumed. 

Traveling  Derrick  Plant  for  4-Span  Arch  Bridge. — The 
bridge  consisted  of  four  7o-ft.  arch  spans  and  was  built  close 
alongside  an  old  bridge  which  it  was  ultimately  to  replace. 
The  approach  from  the  west  was  across  a  wide  flat ;  at  the 
east  the  ground  rose  more  abruptly  from  the  stream.  Condi- 
tions prevented  the  use  of  a  long  spur  trade  and  also  made 
it  necessary  to  install  all  plant  at  and  to  handle  all  material 
from  the  west  bank.  A  diagram  sketch  of  the  arrangement 
adopted  is  shown  by  Fig.  153. 


Fig. 


153. — Sketch  Showing  Traveling  Derrick  Plant  for  Concreting  an  Arch 

Bridge. 


The  track  from  the  west  approached  the  existing  bridge  on 
an  embankment  25  ft.  high.  A  spur  track  175  ft.  long  from 
clear  post  to  end  was  built  'on  trestle  as  shown.  The  cement 
house  and  mixer  platform  were  placed  at  the  foot  of  the  em- 
bankment at  opposite  ends  of  the  spur  track.  Between  the 
two  the  slope  of  the  embankment  was  sheeted  with  i-in. 
boards  and  a  timber  bulkhead  4  ft.  high  was  built  along  the 
toe  of  the  sheeting.  Stone,  sand  and  coal  were  stored  behind 
the  bulkhead  on  the  sheeting.  A  runway  close  to  the  bulk- 
head connected  the  cement  house  with  the  mixer  platform,  all 
materials  to  the  mixer  being  wheeled  in  barrows  on  this  run- 
way. A  «}4~cu'  yd-  Smith  mixer  was  set  on  a  platform  5  ft. 
above  ground  with  its  discharge  end  toward  the  stream.  Be- 
ginning under  this  platform  a  service  track  wa-s  carried  across 
the  flat  and  stream  to  the  extreme  end  of  the  east  abutment. 
This  track  consisted  of  three  rails,  two  rails  4  ft.  apart  next  to 
the  work  and  a  third  rail  25  ft.  from  the  first.  The  4-ft.  gage 


ARCH  AND   GIRDER   BRIDGES.  375 

provided  for  cars  carrying  concrete  buckets  from  the  mixer 
and  the  25-ft.  gage  provided  for  a  traveling  derrick;  i8-lb. 
rails  were  used  and  they  proved  to  be  too  light,  4O-lb.  rails  are 
suggested.  The  derrick  consisted  of  a  triangular  platform 
carrying  a  stiff  leg  derrick  with  a  25-1^  mast  and  mounted  on 
five  wheels.  The  wheels  were  double  flange  16  ins.  diameter 
and  cost  $30  each,  being  the  most  expensive  part  of  the  der- 
rick. The  derrick  was  made  on  the  ground  and  took  four 
carpenters  between  3  and  4  days  to  build.  Derrick  and  350  ft. 
of  service  track,  including  pole  trestle  across  the  stream,  cost 
between  $600  and  $800.  The  derrick  was  moved  by  means  of 
a  cable  wrapped  around  one  spool  of  the  Flory  double-drum 
hoisting  engine  and  leading  forward  and  back  to  deadmen  set 
at  opposite  ends  of  the  service  track.  Cars  carrying  concrete 
buckets  were  run  out  on  the  4-ft.  gage  track  and  the  buckets 
were  hoisted  by  the  derrick  and  dumped  into  a  ^2-cu.  yd.  car 
running  on  a  movable  transverse  track  across  the  bridge. 
This  transverse  track  was  necessary  to  handle  the  concrete 
to  the  far  side  of  the  work,  the  derrick  being  set  too  low  and 
the  boom  being  too  short  to  reach.  The  derrick  was  used  to 
handle  material  excavated  from  the  pier  foundations  and  also 
to  tear  down  the  centers  and  spandrel  forms.  Some  rather 
general  figures  on  the  cost  of  this  bridge  are  given  by  Mr.  H. 
C.  Harrison,  the  contractor.  They  are: 

Materials :  Total. 

6,000  bbls.  cement  at  $2.05 $12,300 

2,500  cu.  yds.  sand  at  $0.80 2,000 

5,000  cu.  yds.  stone  at  $0.85 4,250 

260  M.  ft.  B.  M.  lumber  at  $17 4420 

Total    $22,970 

Labor : 

Cofferdams,  excavation  and  pumping $  3,000 

Forms,  falseworks  and  centers   2,000 

Mixing  and  placing  concrete 4,000 

Placing  reinforcement    4°° 

Removing  falseworks,  forms,  etc 1,200 

One  coat  pitch  and  paper 150 

Building  plant,  etc 2,250 

Total  .  $13.000 


376  CONCRETE    CONSTRUCTION. 

Mr.  Harrison  states  that  including  plant  cost,  delays,  floods 
and  incidentals  the  cost  per  cubic  yard  of  concrete  was  $8  and 
that  excluding  these  items  the  cost  was  $6  per  cu.  yd. 

COST  OF  CONSTRUCTING  CONCRETE  HIGHWAY 
BRIDGE,  GREENE  COUNTY,  IOWA.— The  following  is 
the  itemized  cost  of  constructing  a  reinforced  concrete  slab 
highway  bridge,  one  of  several  built  by  the  Highway  Commis- 
sioners>of  Greene  County,  Iowa,  in  1906.  The  figures  are  given 
by  Messrs.  Henry  Haag  and  D.  E.  Donovan,  the  last  being 
the  foreman  of  the  concrete  gang  doing  the  work.  All  bridges 
consist  of  10  to  12-in.  slabs  reinforced  with  old  steel  rails  and 
of  abutments  and  wing  walls  reinforced  with  old  rods,  bars 
or  angles  selected  from  junk.  This  junk  metal  cost  0.6  cts. 
per  pound  and  the  rails  cut  to  length  cost  1.15  cts.  per  pound 
f.  o.  b.  cars.  The  work  was  done  by  a  special  gang,  the  men 
receiving  $1.50  per  day  and  board.  As  a  rule  the  footings 
were  made  2  ft.  wide  and  as  high  as  need  be  to  get  above  the 
water  and  dirt.  Before  the  footing  concrete  set  steel  rods, 
bars  or  angles  were  placed ;  they  were  long  enough  to  reach 
the  height  of  the  wall  and  3  to  6  ins.  into  the  slab.  The  forms 
for  the  abutment  and  wing  walls  and  for  the  floor  slab  were 
then  erected  complete  before  any  more  concrete  was  placed. 
No  carpenter  was  employed,  every  man  on  the  job  having  been 
taught  to  take  his  certain  place  in  the  work,  then,  the  forms 
being  erected,  every  man  had  his  particular  place  in  the  work 
of  mixing  and  placing  the  concrete.  The  foreman  saw  that 
the  reinforcement  was  properly  placed  and  watched  over  the 
accuracy  of  the  work  generally.  The  concrete  was  allowed  to 
set  on  the  centers  for  from  30  to  40  days ;  the  other  form  work 
was  taken  down  after  three  days  and  travel  over  the  bridge 
permitted  after  three  or  four  days.  The  concrete  was  mixed 
wet.  The  bridge  whose  cost  is  given  was  22  ft.  wide  and  16  ft. 
span  with  2-ft.  wing  walls. 

The  foundations  are  4  ft.  deep  and  2l/2  ft.  wide.  The  walls 
on  top  of  the  foundations  are  7  ft.  high,  18  ins.  wide  at  the 
base,  and  battered  up  to  14  ins.  at  the  top  for  wings  and  12  ins. 
at  top  for  walls.  The  floor  is  22  ft.  by  18  ft.  and  i  ft.  thick.  The 
wheel  guard  is  12  ins.  thick  by  14  ins.  wide  and  32  ft.  long. 
The  itemized  cost  of  this  bridge,  containing  73  cu.  yds.  of  con- 
crete, is  as  follows: 


ARCH  AND   GIRDER   BRIDGES. 


377 


Materials.  Total.             Per  cu.  yd. 

70  cu.  yds.  gravel  at  70  cts $  49.00  $0.6726 

10  cu.  yds.  broken  stone  at  70  cts 7.00  0.0959 

75  bbls.  cement  at  $2.20 165.00  2.2603 

7,000  Ibs.  steel  rails  at  1.15  cts 80.50  1.1027 

1,000  Ibs.  junk  rails  at  0.6  cts 6.00  0.0819 

200  ft.  B.  M.  lumber  wasted  at  $29. . .  5.80  0.0794 

15  Ibs.  nails  at  3  cts 0.45  0.0061 

Labor  and  Supplies : 

2  days'  excavation  at  $14 28.00  0-3835 

24  day  foundation  at  $14 10.00  0.1369 

il/2  days  building  forms  at  $14 21.00  0.2876 

2  days  filling  forms  at  $14 28.00  0.3835 

Hauling  lumber  and  tools 8.00  0.1096 

Hauling  cement  and  tools 18.00  0.2465 

Taking  off  forms 2.30  0.0315 

1,000  Ibs.  coal  at  $4  per  ton 2.00  0.0274 

Total  cost  $431.05  $5.9054 

In  round  figures  the  cost  per  cubic  yard  of  concrete  in  the 
finished  bridge  was  $5.90.  Summarizing  we  nave  the  follow- 
ing cost  per  cubic  yard  of  concrete  in  place : 

Item.  Per  cu.  yd. 

Cement    $2.26 

Steel    - 1.22 

Lumber    0.22 

Gravel  and  stone 0.76 

Labor 1.41 

Coal 0.03 

Total    $5.90 

The  average  cost  of  concrete  in  place  for  all  the  work  done 
in  Greene  County  by  day  labor  was  $6.25  per  cu.  yd.  In  the 
job  itemized  above  the  bank  caved  in,  causing  an  extra  ex- 
pense for  removing  the  earth.  The  gravel  used  in  this  bridge 
was  very  good  clean  river  gravel. 

METHOD  AND  COST  OF  CONSTRUCTING  TWO 
HIGHWAY  GIRDER  BRIDGES.— The  following  account  of 
the  methods  and  costs  of  constructing  two  slab  and  beam 


378  CONCRETE    CONSTRUCTION. 

highway  bridge  decks  on  old  masonry  abutments  is  taken 
from  records  kept  by  Mr.  Daniel  J.  Hauer.  The  first  bridge 
was  a  single  span  15  ft.  long  that  replaced  wooden  stringers 
and  floor  that  had  become  unsafe ;  the  second  was  two  short 
spans  of  a  steel  bridge  that  was  too  light  for  the  traffic  of  the 
road,  and  it  was  torn  down  and  moved  elsewhere,  by  the 
county  authorities.  The  work  was  done  by  contract,  and  in 
each  case  consisted  of  building  the  reinforced  floor  and  girders 
on  the  old  masonry  walls  that  were  in  good  condition.  While 
the  work  was  going  on  traffic  was  turned  off  the  bridges,  fords 
being  used  instead.  Figure  154  shows  a  sketch  of  the  cross- 
section  of  the  floor  and  girders.  In  Example  I  the  girders  had 
a  depth  below  the  floor  of  12  ins.  and  were  of  the  same  width. 
In  Example  II  the  girders  were  14  ins.  wide  and  had  a  depth 
below  the  floor  of  18  ins.  The  floors  on  both  bridges  were 
6  ins.  thick.  Kahn  bars  were  used  for  reinforcement. 


Macadam 


lEN6.-GONTfl. 

Fig.   1C4.— Cross-Section  of  Concrete  Girder  Bridge. 

Example  I. —  This  bridge  was  but  little  more  than  5  ft.  above 
the  stream,  which  was  shallow  and  not  over  7  ft.  wide,  unless 
swollen  by  floods.  The  bottom  for  several  hundred  feet  on 
either  side  of  the  bridge  was  covered  with  coarse  sand  and 
gravel,  that  had  pebbles  in  it  from  the  size  of  a  goose  egg 
down.  Th:?  was  taken  from  the  stream  by  men  with  picks 
and  shovels  and  hauled  to  the  site  of  the  work  with  wheel- 
barrows, and  then  screened  so  as  to  separate  the  gravel  from 
the  sand.  As  it  was  found  that  the  sand  was  so  coarse  that  it 
would  take  more  cement  than  the  specifications  called  for  in  a 
1-2^-5  mixture,  some  much  finer  sand  was  bought  and  mixed 
with  it.  For  the  privilege  of  taking  the  sand  from  the  stream 
$i  was  paid  the  property  owner.  This  was  done  to  get  a  re- 
ceipt and  release  from  him,  rather  than  as  an  attempt  to  pay 
royalty  on  the  gravel  and  sand.  This  dollar  is  included  in  the 
cost  of  the  labor  in  getting  these  materials. 


ARCH   AND   GIRDER   BRIDGES. 


379 


The  cost  of  materials  per  cubic  yard  for  the  bridge  was  as 
given  below,  the  mixture  being  as  stated  above.  The  cement 
cost  $1.40  per  barrel,  delivered  at  the  bridge. 

Per 
Cu.  Yd. 

Steel    $2.50 

Gravel  and  sand    75 

Sand    (bought)     30 

Cement i  .57 

Per   cubic   yard * $5.12 

It  is  of  interest  to  note  the  cost  of  the  gravel  and  sand,  as 
this  includes  the  cost  of  digging  it,  wheeling  it  in  a  wheel- 
barrow an  average  distance  of  100  ft.,  and  then  screening  it 
arid  putting  it  in  two  stock  piles.  The  proportion  of  bought 
sand  used  with  the  creek  sand  was  one-half. 

The  old  wooden  floor  and  stringers  had  to  be  torn  down. 
This  was  done  at  a  cost  of  $1.30  per  M.  ft.  B.  M.,  and  fur- 
nished 60  per  cent,  of  the  lumber  needed  for  forms.  The  floor 
boards  were  3-in,  yellow  pine  planks,  and  the  stringers  6x  12- 
in.  timbers,  rather  heavy,  but  money  was  saved  by  using  them. 
The  6x  12-in.  timbers  were  used  for  props  for  the  centering. 
Additional  lumber  was  bought,  delivered  at  the  site  of  the 
bridge,  for  $20.84  per  M.  ft.  B.  M. 

In  framing  and  erecting  the  forms  the  carpenter  had  labor- 
ers helping  him,  he  doing  only  carpenter's  work,  the  laborers 
carrying  and  lifting  all  pieces  wherever  possible.  The  carpen- 
ter's work  was  about  40  per  cent,  of  the  total  labor  cost,  which 
was  as  follows  per  cubic  yard  of  concrete : 

Tearing  down  old  bridge $0.08 

Lumber    85 

Nails    15 

Labor,  carpenter -77 

Labor,  laborers    96 

$2.81 

The  forms  were  torn  down  by  laborers,  with  the  assistance 
of  a  man  and  his  helper,  who  were  given  the  boards  for  this 
labor  and  to  haul  them  away.  This  reduced  this  item  some- 
what, as  it  only  amounted  to  20  cts.  per  cu.  yd. 


380  CONCRETE    CONSTRUCTION. 

The  cost  of  the  forms  per  thousand  feet  board  measure 
was: 

New  lumber  $20.82 

Nails    1.44 

Labor,  carpenter   7.60 

Labor,  laborers 9.50 

Tearing  down 2.00 

$41.36 

All  the  men,  including  the  carpenter,  worked  10  hours  per 
day,  and  were  paid  at  the  following  rates : 

Carpenter $2-5° 

Sub-foreman    2.00 

Laborers i  .50 

A  regular  foreman  was  not  employed,  but  an  intelligent  and 
handy  workman  was  given  50  cts.  additional  to  lead  the  men 
and  look  after  them  when  the  contractor  was  not  present. 

A  gang  of  six  men  did  the  work  of  mixing  and  placing, 
and  as  the  stock  piles  were  close  by  the  mixing  board  no  extra 
men  were  needed  to  handle  materials.  Water  was  secured 
from  the  stream  in  buckets  for  mixing.  The  mixture  was 
made  very  wet.  The  cost  per  cubic  yard  for  the  entire  struc- 
ture was  as  follows : 

Preparing  for  mixing $0.04 

Cleaning  out  forms 06 

Handling    steel 03 

Mixing  and  placing 1.15 

Ramming 23 


$1.51 

The  cost  of  the  contractor's  expense  of  bidding,  car  fare, 
etc.,  is  listed  under  general  expense,  and  gives  a  total  cost  per 
cubic  yard  of: 

Materials $  5.12 

Erecting  forms 2.81 

Tearing  down  forms 20 

Labor    1.51 

General  expense 2.00 

$11.64 


ARCH  AND   GIRDER   BRIDGES.  381 

Example  II. —  For  this  bridge  both  the  stone  and  sand  had 
to  be  bought.  The  bridge  floor  was  nearly  14  ft.  above  the 
bottom  of  the  stream,  which  was  shallow.  The  wages  paid 
w^re  as  follows  for  a  lo^hour  day: 

Foreman    $3.00 

Laborers 1.50 

Carpenters  were  paid  $3  for  an  8-hour  day  and  time  and  a 
half  for  all  overtime,  which  they  frequently  made. 

For  the  girders  a  1-2-4  mixture  was  used.  The  cement,  de- 
livered at  the  bridge,  cost  $1.21  per  barrel,  there  being  8  cts. 
a  barrel  storage  and  8  cts.  a  barrel  for  hauling  included  in  this. 
The  sand  was  paid  for  at  an  agreed  price  per  cartload  deliv- 
ered, which  averaged  $1.34  per  cu.  yd.  The  stone  was  crushed 
so  as  to  pass  a  ij^-in.  ring  in  all  directions.  It  was  delivered 
at  the  bridge  for  $2.75  per  cu.  yd.  This  makes  the  cost  per 
cubic  yard  for  materials  as  follows : 

Steel    $1.41 

Cement    2.18 

Sand 67 

Stone    2.75 

$7.01 

For  the  floor  a  1-3-5  mixture  was  used,  making  a  cost  for 
material  of: 

Steel .$1.02 

Cement    1.69 

Sand 67 

Stone 2.75 

$6.13 

Two-inch  rough  pine  boards  were  used  to  make  the  troughs 
for  the  girders,  while  i-in.  rough  boards  were  used  for  the 
floors.  These  were  all  supported  by  3  x  4-in.  pine  scantlings. 
This  lumber  cost  delivered  $17.50  per  M.  ft.  B.  M.  Carpenters 
did  all  the  framing,  and  erected  it  with  the  help  of  laborers. 
All  the  carrying  of  the  lumber  was  done  by  laborers.  This 
reduced  the  cost  of  the  work,  as  the  laborers'  wages  amounted 


382  CONCRETE    CONSTRUCTION. 

to  one-third  of  the  whole  cost.  As  soon  as  the  forms  were  all 
in  place,  which  was  before  the  mixing  of  concrete  commenced, 
the  carpenters  were  discharged.  The  cost  per  cubic  yard  for 
forms  was  : 

Lumber    ..................................  ..........  $2.82 

Nails    ................................................  05 

Labor,  carpenters   ......................  .............    1.24 

Laborers    ............................................  62 

$473 

The  tearing  down  of  the  forms  was  done  entirely  by  labor- 
ers at  a  cost  of  61  cts  per  cu.  yd. 

On  concrete  work  it  is  also  advisable  to  keep  the  cost  of 
forms  per  thousand  feet  board  measure,  so  as  to  have  such 
data  for  estimating  on  new  work.  The  cost  per  M.  ft.  on  this 
job  was  : 

Lumber    ...........................................  $17.50 

Nails   ...............................................  30 

Labor,  carpenters    ..................................     7.65 

Laborers    ..........................................     3.85 

Tearing  down  ......................................     3.80 


The  concrete  was  mixed  by  hand,  water  being  carried  in 
buckets  from  the  creek.  Ten  to  twelve  men  were  worked  in 
the  gang  under  a  foreman,  and  the  concrete  was  wheeled 
from  the  mixing  board  to  the  forms  in  wheelbarrows.  The 
mixture  was  made  wet  enough  to  run.  The  cost  per  cubic 
yard  for  the  girders  in  detail  was  as  follows  : 

Foreman    ...........................................  $0.41 

Preparing  for  mixing  ................................  0.14 

Cleaning  out  forms  ..................................  0.07 

Handling  materials  ..................................  0.30 

Handling  and  placing  steel  ...........................  0.40 

Mixing  and  placing  ............................  ....  0.87 

Ramming    ....................................  ......  0.45 

$2.64 


ARCH   AND   GIRDER   BRIDGES.  383 

The  cost  of  labor  for  the  floor  was : 

Foreman    $0.28 

Preparing  for  mixing 0.08 

Cleaning  out  forms 0.05 

Handling  materials   0.14 

Handling  and  placing  steel 0.08 

Mixing  and  placing 0.87 

Ramming 0.36 


$1.86 

This  gives  a  total  cost  per  cubic  yard  for  the  concrete  in  the 
girders  in  the  completed  bridge  as  follows: 

Materials    $  7.01 

Erecting  forms 4.73 

Tearing  down  forms  0.61 

Labor    2.57 

General   expense    1.60 

$16.52 
The  cost  per  cubic  yard  for  the  floor  was: 

Materials    $  6. 1 3 

Erecting  forms 4.73 

Tearing  down  forms 0.61 

Labor    i  .86 

General   expense    1.60 

$14.93 

Included  with  this  is  an  item  for  general  expense,  being  ex- 
penses of  the  contractor  in  bidding  on  the  work,  car  fare,  and 
other  items  of  expense  in  looking  after  the  contract. 

It  will  be  noticed  that  a  record  is  here  given  of  three  differ- 
ent mixtures  and  that  the  labor  cost  of  mixing  and  placing  in- 
creases with  the  richness  of  the  mixture.  This  is  because  it 
takes  a  greater  number  of  batches  to  the  cubic  yard.  Record 
has  also  been  given  of  cost  of  preparing  the  mixing  board  and 
other  work  necessary  to  start  and  clean  up  each  day;  also 
when  stock  piles  could  not  be  arranged  close  to  the  mixing 
board,  of  the  cost  of  handling  the  materials.  These  items, 
it  will  be  noticed,  are  large  enough  to  be  considered  in  esti- 


384  CONCRETE    CONSTRUCTION. 

mating  on  new  work.  The  cost  of  sweeping  and  cleaning  out 
the  forms  has  also  been  listed,  as  this  work  is  extremely 
important. 

The  cost  of  the  reinforcing  steel  is  given  in  with  the  ma- 
terials, but  the  labor  of  handling  it  and  placing  it  in  the  forms 
is  listed  under  labor.  This  naturally  varies  with  the  amount 
of  steel  needed,  and  with  the  Kahn  bar  it  will  vary  from  10  cts. 
to  75  cts.  per  cubic  yard,  as  the  prongs  of  the  bar  must 'be  bent 
into  proper  position  and  at  times  straightened,  when  bent  in 
shipment.  This  cost  seems  large,  but  it  is  done  with  the 
ordinary  labor,  while  with  round  rods  a  large  amount  of 
blacksmith  work  has  to  be  done  and  a  smith  and  his  helper 
frequently  must  place  them.  The  patent  bars  are  all  lettered 
and  numbered  as  structural  steel  is,  and  can  be  placed  under 
the  direction  of  the  foreman. 

One  striking  lesson  can  be  learned  from  the  forming.  It 
will  be  noticed  that  the  cost  for  common  labor  for  handling 
and  helping  to  erect  the  forms  was  much  larger  in  Example  I 
than  in  Example  II,  although  the  bridge  was  higher  in  the  lat- 
ter instance.  This  was  caused  by  the  heavy  timber  that  was 
used,  and  equaled  an  extra  cost  nearly  50  per  cent,  of  the  price 
of  new  lumber.  It  certainly  speaks  volumes  against  the  use 
of  unnecessarily  heavy  timber  for  concrete  forms. 

In  bridge  work  the  height  of  the  floor  above  the  stream  to 
some  extent  governs  the  cost  of  the  forms.  This  is  made  so 
by  the  extra  lumber  needed  as  props  or  falsework  to  support 
the  forming,  and  also  by  the  fact  that  men  at  some  height 
above  the  ground  do  not  work  as  quickly  or  as  readily  as  they 
do  nearer  the  ground.  For  high  and  long  spans  a  derrick  is 
sometimes  needed  for  the  work  of  placing  the  centering. 

On  these  jobs,  the  concrete  was  made  so  wet  that  with  the 
proper  tamping  and  cutting  of  the  concrete  in  the  forms  the 
surfaces  were  so  smooth  that  no  plastering  was  needed. 

MOLDING    SLABS    FOR    GIRDER    BRIDGES.— The 

bridges  carry  railway  tracks  across  intersecting  streets;  the 
slabs  rest  on  two  abutments  and  three  rows  of  columns  so 
that  there  are  two  24^4 -ft.  spans  over  the  street  roadway  and 
one  io^4 -ft.  span  over  each  sidewalk.  The  larger  slabs  were 
24  ft.  3  ins.  long,  33  ins.  thick  and  7  ft.  wide ;  each  contained 


ARCH  AND   GIRDER  BRIDGES. 


385 


cu.  yds.  of  concrete  and  weighed  36%  tons.  The  smaller 
slabs  were  10  ft.  9  ins.  long,  17  ins.  thick  and  7  ft.  wide;  each 
contained  3.65  cu.  yds.  of  concrete  and  weighed  7.8  tons.  The 
weights  were  found  by  actual  weighing.  They  make  .the 
weight  of  the  reinforced  slab  between  160  and  162  Ibs.  per 
cu.  ft.  The  concrete  was  generally  i  part  cement  and  4  parts 


DDoaQaaoDoaaao 


DQDaaaDaaaaaaQ 

Fig.   155.— Arrangement  of  Tracks  and  Forms  for  Molding  Slabs  for  Girder 

Bridge. 

pit  gravel.     The  reinforcement  consisted  of  corrugated  bars. 
The  method  of  molding  was  as  follows : 

A  cinder  fill  yard  was  leveled  off  and  tamped,  then  the  forms 
were  set  up  on  both  sides  of  two  lines  of  railway  track  ar- 
ranged as  shown  by  Fig.  155.  The  exact  construction  of  the 


End  View,  Side  E/evot/on. 

Fig.    156.— Form    for    Molding    Slabs    for    Girder    Bridge. 

forms  for  one  of  the  larger  slabs  is  shown  by  Fig.  156.  The 
side  and  end  pieces  were  so  arranged  as  to  be  easily  taken 
down  and  erected  for  repeated  use.  About  100  floors  were 
used  and  they  had  to  be  leveled  up  each  time  used  as  the 
lifting  of  the  hardened  slab  disarranged  them.  The  side  and 


386  CONCRETE    CONSTRUCTION. 

end  pieces  were  removed  in  about  a  week  or  ten  days,  but 
the  slabs  stood  on  the  floor  90  days,  being  wetted  each  day 'for 
two  weeks  after  molding. 

The  plant  for  mixing  and  handling  the  concrete  was 
mounted  on  cars.  A  flat  car  had  a  rotary  drum  mixer  mounted 
on  a  platform  at  its  forward  end.  Beneath  the  mixer  was  a 
hopper  provided  with  a  deflector  which  directed  the  concrete 
to  right  or  left  as  desired.  Under  the  hopper  were  the  ends 
of  two  inclined  chutes  extending  out  sidewise  beyond  the  car 
— one  to  the  right  and  one  to  the  left — and  over  the  slab 
molds  on  each  side.  Above  the  mixer  was  another  platform 
containing  a  charging  hopper,  and  from  the  rear  of  this  plat- 
form an  incline  ran  down  to  the  rear  end  of  the  car  and  then 
down  to  the  track  rails.  A  car  loaded  with  cement  and  gravel 
in  the  proper  proportions  was  hauled  up  the  incline  by  cable 
operated  by  the  mixer  engine,  until  it  came  over  the  topmost 
hopper  into  which  it  was  dumped.  This  hopper  directed  the 
charge  into  the  mixer  below ;  the  mixer  discharged  its  batch 
into  the  hopper  beneath  from  which  it  flowed  right  or  left  as 
desired  into  one  of  the  chutes  and  thence  into  the  mold.  The 
chutes  reached  nearly  the  full  length  of  the  molds  and  dis- 
charged as  desired  over  the  ends  into  the  far  end  of  the  mold 
or  through  a  trap  over  the  end  of  the  mold  nearest  the  car. 

To  the  rear  of  the  mixer  car  came  a  cement  car  provided 
with  a  platform  overhanging  its  forward  end.  Two  hoppers 
were  set  in  this  platform  each  holding  a  charge  for  one  batch. 
Coupled  behind  the  cement  cars  came  three  or  four  gravel 
cars.  These  were  gondola  cars  and  plank  runways  were  laid 
along  their  top  outer  edges  making  a  continuous  runway  for 
wheelbarrows  on  each  side  from  rear  of  train  to  front  of 
cement  car.  The  sand  and  gravel  were  wheeled  to  the  two 
measuring  hoppers  and  the  cement  was  handed  up  from  the 
car  below  and  added,  the  charge  was  then  discharged  into  the 
dump  car  below  and  the  car  was  hauled  up  the  incline  to  the 
mixer  as  already  described.  Two  measuring  hoppers  were 
used  so  that  one  was  being  filled  while  the  other  was  emptied, 
thus  making  the  work  continuous. 

The  molding  gang  consisted  of  33  laborers,  two  foremen  and 
one  engineman.  This  gang  averaged  7  of  the  large  slabs  per 
10-hour  da>  and  at  times  made  as  many  as  9  slabs.  When 


ARCH   AND   GIRDER   BRIDGES.  387 

molding  small  slabs  an  average,  of  12  were  made  per  day.  This 
record  includes  all  delays,  moving  train,  switching  gravel  cars 
on  and  off,  building  runways,  etc.  The  distribution  of  the 
men  was  about  as  follows : 

Handling  Materials  :  No.  Men. 

Shoveling  gravel  into  wheelbarrows 9 

Wheeling  gravel  to  measuring  hoppers .9 

Emptying  cement  into  measuring  hoppers 2 

Handling  cement  to  men  emptying .....;*•  .-~i :  • 

In  charge  of  loading  dump  car I 

On  top  of  cement  car I 

Sub-foreman  in  charge I 

Mixing  and  Placing: 

Engineer I 

In  charge  of  mixer I 

Hoeing  and  spreading  in  mold 2 

Spading  in  mold '  2L 

Finishing  sides  of  block •   2 

General  laborers   3 

Foreman  in  charge I 

Total  men 36 

This  gang  mixed  and  placed  concrete  for  7  blocks  or  H7I4 
cu.  yds.  of  concrete  per  day.  Assuming  an  average  wage  of 
$2  per  day  the  cost  of  labor  mixing  and  placing  was  61.4  cts. 
per  cu.  yd.  or  $10.28  per  slab.  It  is  stated  that  the  slabs  cost 
$n. 80  per  cu.  yd.  on  storage  pile.  This  includes  labor  and 
materials  (concrete  and  steel)  ;  molds ;  loading  into  cars  with 
locomotive  crane,  hauling  cars  to  storage  yard  and  unloading 
with  crane  into  storage  piles,  and  inspection,  incidentals,  etc. 
To  load  the  slabs  into  cars  from  storage  piles,  transport  them 
to  the  work  and  place  them  in  position  is  stated  to  have  cost 
$2  per  cu.  yd.  The  slabs  were  placed  by  means  of  a  locomo- 
tive crane  being  swung  from  the  flat  cars  directly  into  place._ 

METHOD  AND  COST  OF  CONSTRUCTING  CON- 
NECTICUT AVE.  BRIDGE,  WASHINGTON,  D.  C.— The 
Connecticut  Ave.  Bridge  at  Washington,  D.  C.,  consists  of 
nine  I5o-ft.  spans  and  two  82-ft.  spans,  one  at  each  end,  all 
full  centered  arches  of  mass  concrete  trimmed  with  tool- 
dressed  concrete  blocks.  Figure  157  is  a  part  sectional  plan 


CONCRETE    CONSTRUCTION. 


Fig.    157,— Sections   Showing  Construction  of  Connecticut  Ave.   Bridge. 


ARCH  AND   GIRDER   BRIDGES.  389 

and  elevation  of  the  bridge,  showing  both  the  main  and 
spandrel  arch  construction.  This  bridge  is  one  of  the  largest 
concrete  arch  bridges  in  the  world,  being  1,341  ft.  long  and 
52  ft.  wide,  and  containing  80,000  cu.  yds.  of  concrete.  Its 
total  cost  was  $850,000  or  $638.85  per  lin.  ft.,  or  $10.63  per 
cu.  yd.  of  masonry.  It  was  built  by  contract,  with  Mr.  W.  J. 
Douglas  as  engineer  in  charge  of  construction.  The  account 
of  the  methods  and  cost  of  construction  given  here  has  been 
prepared  from  information  obtained  from  Mr.  Douglas  and  by 
personal  visits  to  the  work  during  construction. 

General  Arrangement  of  the  Plant. — The  quarry  from  which 
the  crushed  stone  for  concrete  was  obtained  was  located  in  the 
side  of  the  gorge  at  a  point  about  400  ft.  from  the  bridge.  In- 
cidentally, it  may  be  added,  the  fact  that  the  contractor  had  an 
option  on  this  quarry  gave  him  an  advantage  of  some  $30,000 
over  the  other  bidders.  The  stone  from  the  quarry  was  hoisted 
about  50  ft.  by  derricks  and  deposited  in  cars  which  traveled 
on  an  incline  to  a  Gates  gyratory  crusher,  into  which  they 
dumped  automatically.  The  stone  from  the  crusher  dropped 
into  a  6oo-cu.  yd.  bin  under  the  bottom  of  which  was  a  tunnel 
large  enough  for  a  dump  car  and  provided  with  top  gates  by 
which  the  stone  above  could  be  dropped  into  the  cars.  The 
cars  were  hauled  by  cable  to  the  mixer  storage  bin  and  there 
discharged.  Sand  was  brought  in  by  wagons  and  dumped 
onto  a  platform  about  50  ft.  higher  than  the  bottom  of  the 
main  stone  bin.  A  tunnel  exactly  similar  to  that  under  the 
stone  bin  was  carried  under  the  sand  storage  platform.  The 
sand  car  was  hauled  from  this  tunnel  by  cable  to  the  mixer 
storage  bin  using  the  same  cable  as  was  used  for  the  stone 
cars,  the  cable  being  shifted  by  hand  as  was  desired.  Cement 
was  delivered  to  the  mixer  platform  from  the  crest  of  the  bluff 
by  means  of  a  bag  chute. 

The  mixer  used  was  one  of  the  Hains  gravity  type.  It 
had  four  drops  and  was  provided  with  four  mixing  hoppers  at 
the  top.  The  concrete  was  made  quite  wet.  The  proportions 
of  sand  and  water  were  varied  to  suit  the  stone  according  to 
its  wetness  and  the  percentage  of  dust  carried  by  it.  The  head 
mixer  regulated  the  proportions  and  his  work  was  checked  by 
the  government  inspector.  From  the  bottom  hopper  the 
mixed  concrete  dropped  into  a  skip  mounted  on  a  car. 


390 


CONCRETE    CONSTRUCTION. 


To  distribute  the  skip  cars  along  the  work  a  trestle  was  built 
close  alongside  the  bridge  and  at  about  springing  line  level. 
This  trestle  had  a  down  grade  of  about  2  per  cent,  from  the 


Fig.   158, — Center  for  Connecticut  Ave.  Bridge   (Elevation). 

mixer.  Derricks  mounted  along  the  centering  and  on  the 
block  molding  platform  lifted  the  skips  from  the  cars  and  de- 
posited them  where  the  concrete  was  wanted.  The  skip  cars 


ARCH  AND   GIRDER   BRIDGES. 


391 


were  large  enough  for  three -skips  but  only  two  were  carried 
so  that  the  derricks  could  save  time  by  depositing  an  empty 
skip  in  the  vacant  space  and  take  a  loaded  skip  away  with  one 


Fig.    158.— Center   for   Connecticut   Ave.    Bridge    (Details). 

full  swing  of  the  boom.  Altogether  nine  derricks  were  used 
in  the  bridge,  four  having  7o-ft.  booms  and  five  having  QO-ft. 
booms.  These  derricks  were  jacked  up  as  the  work  pro- 
gressed. 


392  CONCRETE    CONSTRUCTION. 

Forms  and  Centers. — The  forms  for  wall  and  pier  work 
consisted  of  i-in.  lagging  held  in  place  by  studs  about  2  ft.  on 
centers  and  they  in  turn  supported  by  wales  which  were  con- 
nected through  the  walls  by  bolts,  the  outer  portions  of  which 
were  removed  when  the  forms  were  taken  down. 

The  centers  for  the  five  i5O-ft.  arches  were  all  erected  at  one 
time ;  those  for  the  82-ft.  arches  were  erected  separately.  The 
seven  centers  required  1,500,000  ft.  B.  M.  of  lumber  or  1,404 
ft.  B.  M.  per  lineal  foot  of  bridge  between  abutments,  or  1,640 
ft.  B.  M.  per  lineal  foot  of  arch  span.  The  centers  for  the 
main  arch  spans  are  shown  in  detail  by  Fig.  158;  this  drawing 
shows  the  sizes  of  all  members  and  the  maximum  stresses  to 
which  they  were  subjected  from  the  loading  indicated,  that  is 
the  arch  ring  concrete.  The  centers  as  a  rule  rested  on  pile 
foundations.  Four  piles  to  each  post  were  used  for  the  inter- 
mediate posts  and  two  piles  for  the  posts  in  the  two  rows  next 
the  piers.  Concrete  foundations,  however,  were  put  in  Rock 
Creek  and  on  the  line  of  Woodley  Lane  Bridge  where  it  was 
impracticable  to  drive  piles.  As  considerable  difficulty  was  ex- 
perienced in  driving  the  piles,  the  ground  consisting  mostly  of 
rotten  rock,  it  is  thought  that  it  would  have  cost  less  if  the 
contractor  had  used  concrete  footings  throughout. 

Some  of  the  costs  of  form  work  and  centering  are  given. 
The  cost  of  lumber  delivered  at  the  bridge  site  was  about  as 
follows : 

M.ft.  B.  M. 

Rough  Virginia  pine $25 

Dressed  Virginia  pine  lagging v 23 

Rough  Georgia,  sizes  up  to  12x12  ins 33 

Rough  Georgia,  sizes  over  12x12  ins 35 

Rough  oak  lumber 35 

The  following  wages  were  paid  :  Foreman  carpenter,  $3.50; 
carpenters,  $2  to  $3;  laborers,  $1.70,  with  a  few  at  $1.50.  An 
8-hour  day  was  worked. 

The  cost  of  form-work  is  given  in  summary  as  follows : 
Lagging  per  M.  ft.  (used  twice)  : 

Lumber  at  $23 $11.50 

Erection   15.00 

Total  cost  erected $26.50 


ARCH  AND   GIRDER   BRIDGES.  393 

Studding  and  rough  boards  used  in  place  of  lagging  per  M. 
ft.  (used  twice)  : 

Lumber  at  $25 $12.50 

Erection   '...... 10.00 

Total  cost  erected $22.50 

Wales  per  M.  ft.  (used  six  times)  : 

Lumber  at  $36 $  6.00 

Erection   Io.oo 

Total  cost  erected $16.00 

The  total  cost  of  the  main  arch  span  centers  to  the  District 
of  Columbia  was  $54,000  or  $59  per  lineal  foot  of  arch  span, 
or  $37-33  Per  M.  ft.  B.  M.  he  cost  of  center  erection  and 
demolition  was  as  follows : 

Erection  below  springing  line  per  M.  ft $15 

Erection  above  springing  line  per  M.  ft 25 

Demolition    "5 

The  salvage  on  the  centers  amounted  to  $11  per  M.  ft.  B.  M. 

The  spandrel  arch  centers  were  each  used  twice  arid  cost 
per  M.  ft.  B.  M.  for 

Lumber  at  $25  per  M.  ft $12.50 

Erecting  at  $25  per  M.  ft 25.00 

Moving  at  $5  per  M,  ft 5.00 

Total  per  M  ft 42.50 

Molding  Concrete  Blocks. — The  bridge  is  trimmed  through- 
out with  molded  concrete  blocks,  comprising  belt  courses, 
quoin  stones,  chain  stones,  ring  stones,  brackets  and  dentils. 
The  blocks  were  made  of  a  1-2-4^/2  concrete  faced  with  a  1-3 
mixture  of  Dragon  Portland  cement  and  bluestone  screenings 
from  2^-in.  size  to  dust.  They  were  cast  in  wooden  molds 
with  collapsible  sides  held  together  by  iron  rods.  Each  mold 
was  provided  with  six  bottoms  so  that  the  molded  block  could 
be  left  standing  on  the  bottom  to  harden  while  the  side  pieces 
were  being  used  for  molding  another  block.  The  molding  was 
done  on  a  perfectly  level  and  tight  floor  on  mud  sills,  the  per- 
fect level  of  the  molding  platform  having  been  found  to  be  an 
important  factor  in  securing  a  uniform  casting.  The  blocks 
were  molded  with  the  principal  showing  face  down  and  the 
secondary  showing  faces  vertical.  The  facing  mortar  was 


394  CONCRETE    CONSTRUCTION. 

placed  first  and  then  the  concrete  backing.  Care  was  taken 
to  tamp  the  concrete  so  as  to  force  the  concrete  stone  into  but 
not  through  the  facing.  Mr.  Douglas  remarks  that  the  back 
of  the  block  should  always  be  at  the  top  in  molding  since  the 
laitance  or  slime  always  flushes  to  the  surface  making  a  weak 
skin  which  will  develop  hair  cracks.  In  this  work  the  backs 
of  the  blocks  were  mortised  by  embedding  wooden  cubes  in 
the  wet  concrete  and  removing  them  when  the  concrete  had 
set.  These  mortises  bonded  the  blocks  with  the  mass  con- 
crete backing.  The  blocks  were  left  to  harden  for  at  least  30 
days  and  preferably  for  60  days  and  were  then  bush  hammered 
on  the  showing  faces,  some  of  the  work  being  done  by  hand 
and  some  with  pneumatic  tools. 

Some  precautions  necessary  in  the  molding  and  handling  of 
large  concrete  blocks  were  discovered  in  this  work  and  merit 
mention.  In  designing  blocks  for  molding  it  is  necessary 
to  avoid  thin  flanges  or  the  flanges  will  crack  and  break  off ; 
blocks  molded  with  a  2*4 -in.  flange  projecting  i^4  ins.  gave 
such  trouble  from  cracking  on  this  work  that  a  flange  5  ins. 
thick  was  substituted.  Provide  for  the  method  of  handling 
the  block  so  that  dog  or  lewis  holes  will  not  come  in  the  show- 
ing faces.  Dog  holes  can  be  made  with  a  pick  when  the  con- 
crete is  three  or  four  weeks  old.  When  it  is  not  practicable  to 
use  dogs,  two-pin  lewises  can  be  used.  The  lewis  holes  should 
be  cast  in  the  block  and  should  be  of  larger  size  than  for 
granite;  they  should  not  be  located  too  near  the  mortar  faces. 
In  turning  blocks  it  is  necessary  to  provide  some  sort  of 
cushion  for  them  to  turn  on  or  broken  arrises  will  result. 
When  the  work  will  permit,  it  is  desirable  to  round  the  arrises 
J:o  about  a  ^-in.  radius. 

The  following  general  figures  of  the  cost  of  block  work  are 
available.  Foreman  cutters  were  paid  $5  per  day;  foreman 
concrete  workers  $3  per  day ;  stonecutters  $4-  per  day ;  con- 
crete laborers  $1.70  per  day,  and  common  laborers  $1.50  to 
$1.70  per  day.  Plain  and  ornamental  blocks  cost  about  the 
same,  the  large  size  of  the  ornamental  blocks  bringing  down 
the  cost.  The  following  is  given  as  the  average  cost  of  block 
work  per  cubic  yard : 


ARCH  AND   GIRDER  BRIDGES. 


395 


Cement $  1.95 

Sand 0.35 

Stone 1.14 

Forms,  lumber  and  making 0.80 

Mixing  and  placing  concrete 1.50 

Dressing    4.73 

Handling  and   setting 2.00 

Superintendence,  plant,  incidentals  at  25  per  cent 3.12 

Condemnation  at  5  per  cent 0.78 

Total  cost  blocks  in  place $16.37 

It  will  be  seen  that  the  largest  single  item  in  the  above  sum- 
mary of  costs  is  the  item  of  dressing.  This  was  done,  as  stated 
above,  partly  by  hand  and  partly  by  pneumatic  tools.  Hand 
tooling  cost  about  twice  as  much  as  machine  tooling,  but  its 
appearance  was  generally  better.  The  average  cost  of  tooling 
the  several  forms  of  blocks  is  shown  by  Table  XIX.  For 
42,190  sq.  ft.  the  average  cost  was  26  cts.  per  sq.  ft.  or  $2.34 
per  sq.  yd.,  or  $4.73  per  cu.  yd.  of  block  work.  This  tooling 
'was  done  by  stone  cutters,  and  was  unusually  high  in  cost. 

Mass  Concrete  Work. — All  parts  of  the  bridge  except  the 
molded  block  trim  were  built  of  concrete  deposited  in  place. 
Briefly,  the  molded  blocks  were  set  first  and  then  backed  up 
with  the  mass  concrete  deposited  in  forms  and  on  centers. 
The  only  features  of  this  work  that  call  for  particular  descrip- 
tion are  those  in  connection  with  the  main  arch  ring  and  the 
spandrel  arch  construction. 

The  main  arch  rings  were  concreted  in  transverse  sections ; 
Fig.  158  shows  the  size  and  order  of  construction  of  these  sec- 
tions. Back  forms  were  necessary  up  to  an  angle  of  45°  from 
the  spring  line  after  which  the  concrete  was  made  somewhat 
drier  and  back  forms  were  not  used.  After  Sections  i,  2,  3  and 
4  had  been  concreted  they  were  allowed  to  set  and  then  the 
struts  and  back  forms  were  taken  out  and  the  intervening 
sections  were  concreted.  The  large  Sections  6  and  7  were  con- 
creted in  five  sections  each,  in  order  to  permit  the  taking  out 
of  the  timber  struts  supporting  the  sections  above.  The  con- 
crete in  all  sections  was  placed  in  horizontal  layers  as  a  rule 
and  it  is  the  judgment  of  the  engineers  in  charge  of  this  work 
that  this  is  the  preferable  method. 


396 


CONCRETE    CONSTRUCTION. 


TABLE  XIX. — SHOWING  COST  OF  TOOLING  CONCRETE  ORNAMENTAL  BLOCKS  FOR 
CONNECTICUT  AVENUE  BRIDGE. 


Per  Cubic  Foot. 

Per  Superficial  Foot  of 
Showing  Face. 

DESCRIPTION. 

1 

03 

45  «s 

1 

i 

1 

i 

u 
<£ 

8 

JO--2 

1:  2:  4£  Concrete  Backing. 
1:  3   (Mortar  Face) 

Id 

•§ 

y 
«-•    . 

o 

1 

| 

1 

nl 

4 

£«, 

0 

<^>2 

tfSrd 

C/3 

O.^ 

£u 

11 

B  ^ 
I.S 

3* 

£3 

11 

ll 

3*1 

(21 

9 

s§ 

|| 

Brackets  under  Lamps  and  Rail  Posts 

(Cap  and  Base)  

344 

16.0 

5,500 

$0.27 

10.5 

3,630 

$0.41 

0  66 

770 

5  9 

4  560 

0  30 

3  8 

2  930 

0  47 

0  64 

520 

5  5 

2  860 

0  20 

8  0 

4  160 

0  14 

1  45 

494 

61  2 

30*220 

0  12 

35  4 

17  490 

0  21 

0  58 

Pedestal  (3  courses) 

162 

27  2 

4  400 

0  15 

14  1 

2  290 

0  29 

0  52 

Rail  Posts  (Top  and  Base)  

296 

7.1 

2,100 

0.50 

17.3 

5,100 

0.21 

2.43 

Lamp  Posts  and  Parapets  over  Piers 

(Top  and  Base)  

248 

22.9 

5,690 

0  17 

26  5 

6  580 

0  15 

1  16 

Average  of  above  —        Totals.  .  . 

2,834 

19.5 

55,330$0.17i 

14.8 

43,190 

$0.26 

0.77 

1 

1 

TABLE  XX. — SHOWING  COST  OF  MASS  CONCRETE  WORK  PER  CUBIC  YARD. 


DESCRIPTION. 

Proportions. 

Average  Yardage 
for  Day's  Run. 

Cost 
Delivered 
on 
Mixer. 

Materials. 

Cost  of 
Mixing 
and 
Placing. 

Mixing  and  Placing. 

Cost  of 
Form  Work. 

^ 
1 

1 

i 

^ 

*' 
•H 

f 
If 

1! 

$3.80 
3.66 
3.70 
5.18 
5.42 
5.48 
3.65 
2.90 

Cement. 

T3 

i 

M 

% 

M 

C 

S 
a 

Lumber. 

5 

C/3 

1.08 
1.08 
1.23 
1.23 
1.23 
1.2d 
1.23 
1.30 

rt 

2 

X 

i 

M 

Oi 

3 

£ 

o 

fj 

W 

Class  A  in  Piers.  .  .  . 

1-2  :4i 

150 
200 
160 
110 
110 
200 
150 
145 

1.65 
1.65 
1.40 
1.40 
1.40 
1.40 
1.40 
0.90 

0.39 
0.39 
0.42 
0.42 
0.42 
0.42 
0.42 
0.3, 

3.12 
3.11 
3.05 
3.05 
3.05 
3.05 
3.05 
2.51 

0.09 
0.05 
0.09 
0.11 
0.11 
0.07 
0.11 

o.n 

0.21 
0.28 
0.18 
0.36 
D.40 
0.26 
3.24 
3.28 

0.30 
0.33 
0.27 
0.47 
0.51 
0.33 
0.35 

039 

0.17 
0.08 
0.17 
0.77 
0.85 
0.94 
0.10 
0.00 

0.05 
0.03 
0.05 
0.25 
0.28 
0.30 
0.03 
0.00 

0.16 
0.10 
0.16 
0.64 
0.73 
0.86 
0.12 
0.00 

0.38 
0.21 
0.38 
1.66 
1.86 
2.10 
0.25 

Class  A  in  Arches  

1:2  :4i 

Class  B,  in  Piers—  Solid 
Work  
Class  B,  in  Piers  —  Hol- 
low Work  

1:3:6 
1:3:6 
1:3:6 
1:3:6 
1:3:6 
1:3:10 

Class  B,  in  Spandrel 
Walls  

Class  B,  in  Spandrel 
Arches 

Class  B,  in  Abutments..  . 
Class  C,  Filling  over 
Bridge  

*Add  25%  to  the  cost  here  tabulated  for  superintendence,  plant  and  incidentals. 

Considerable  difficulty  was  experienced  in  building  the  large 
arches  with  a  concrete  block  facing  on  account  of  the  fact 
that  the  edges  of  the  blocks  are  liable  to  chip  off  when  any 
concentrated  pressure  is  brought  on  them.  In  order. to  permit 
the  ring  of  blocks  to  deform  as  the  centering  settled  under  its 


ARCH  AND   GIRDER   BRIDGES.  397 

load,  sheet  lead  was  placed  in  the  joints  between  blocks  at  the 
points  corresponding  with  the  construction  joints  between 
sections  of  the  mass  concrete  backing.  The  deflection  of  the 
centers  at  the  crown  was  a  maximum  of  3^4  ins.  and  a  mini- 
mum of  2T/2  ins. 

The  centering  of  the  main  arches  was  not  struck  until  the 
spandrel  arches  and  all  the  work  above  the  main  arches  to  the 

TABLE    XXI — Detail    Cost    of   Engineering    and  Inspection   for   Different 

Classes  of  Work. 

Engineering.  Inspection. 

Kind  of  Work.                                      Total.  Unit.  Total.      Unit. 

Class  A,  concrete,  23,500  cu.  yds $3,055.00  $0.13  $1,762.50    $0.075 

Class  B,  concrete,  36,580  cu.  yds. .......  3,658.00  o.io  1,646.10      0.045 

Class  C,  concrete,  2,150  cu.  yds 107.50  0.05  53.75      0.025 

Class  D,  concrete,  6,250  cu.  yds 1,875.00  0.30  4,687.50      0.75 

1,000  M.  ft.  B.  M.  centering 1,000.00  i.oo  440.00      0.44 

Cement,  73,000  barrels 365.00  0.005  73O.oo      o.oi 

Earth  filling,  50,000  cu.  yds 1,000.00  0.02  ,  500.00      o.oi 

bottom  of  the  coping  had  been  completed.  The  first  and  third 
spandrel  arch  on  each  side  of  the  piers  was  made  with  an 
expansion  joint  in  the  crown.  To  permit  further  of  the  adjust- 
ment of  the  portion  of  the  masonry  above  the  backs  of  the 
main  arches,  the  crown  of  the  middle  arch  of  each  set  of  span- 
drel arches  was  left  unconcreted  until  the  center  of  the  main 
arches  had  been  struck.  It  may  be  noted  here  that  the  expan- 
sion joints  in  the  first  and  third  arches  were  carried  up 
through  the  dentils  and  coping,  and  observations  show  that 
these  joints  are  about  l/%  in.  larger  in  winter  than  in  summer. 

The  cost  of  the  mass  concrete  work  is  shown  in  Table 
XX.  These  figures  are  based  on  the  wages  already  quoted 
and  the  following:  Foreman  riggers,  $4.50;  riggers,  $1.50  to 
$1.75  and  $2;  skilled  laborers,  $2;  engineers,  $3.50.  The 
detail  cost  of  engineering  and  inspection  is  shown  in  Table 
XXI. 

ARCH  BRIDGES,  ELKHART,  IND.— At  the  new  Elk- 
hart,  Ind.,  yards  of  the  Lake  Shore  &  Michigan  Southern  Ry. 
the  tracks  are  carried  over  a  city  street  by  concrete  arches 
40,  60  and  160  ft.  long.  These  arches  all  have  a  span  of  30  ft., 
a  height  of  13  ft.  and  a  ring  thickness  at  crown  of  28  ins.  The 


398  CONCRETE    CONSTRUCTION. 

reinforcement  consists  of  arch  and  transverse  bars;  the  arch 
bars  are  spaced  6  ins.  on  centers  2l/2  ins.  from  both  extrados 
and  intrados,  and  the  transverse  bars  are  spaced  24  ins.  on 
centers  inside  both  lines  of  arch  bars.  The  proportions  of  the 
concrete  were  generally  i  cement,  3  gravel  and  6  stone.  The 
gravel  was  a  material  dug  from  the  foundations  and  was  about 
50  per  cent,  sand  and  50  per  cent,  gravel,  ranging  up  to  the 
size  of  pigeons'  eggs.  The  concrete  was  machine  mixed  and 
was  mixed  very  wet. 

The  work  was  done  by  the  railway  company's  forces,  and 
Mr.  Samuel  Rockwell,  Assistant  Chief  Engineer,  gives  the 
following  figures  of  cost : 

Cost. 

Total.         Per  cu.  yd. 
Temporary  buildings,  trestles,  etc..  .  .$      752.33  $0.15 

Machinery,  pipe  fittings,  etc 416.34  0.08 

Sheet  piling  and  boxing 1,006.12  0.21 

Excavation  and  pumping 1,619.74  0.33 

Arch  centers  and  boxing 3,528.92  0.73 


Total    $7.32345  $I-5° 

Concrete  masonry : 

Cement    8,860.55  J-84 

Stone    i  ,788.50  0.36 

Sand    240.00  0.05 

Drain  tile 103-03  0.02 

Labor    8,091.41  1.68 


Total  concrete   $19,083.49  $3-95 

Steel  reinforcing  rods $  3,028.39  $0.63 

Engineering,  watching,  etc 508.40  o.n 


Grand  total  (4,833  cu.  yds.  con- 
crete)      $29,943.73  $6.19 

ARCH  BRIDGE,  PLAINWELL,  MICH.— The  following 
figures  of  cost  of  a  reinforced  concrete  arch  bridge  are  given 
by  Mr.  P.  A.  Gourtright.  The  bridge  crosses  the  Kalamazoo 
River  at  Plainwell,  Mich.,  and  is  446  ft.  long  over  all  with 
seven  arches  of  54  ft.  span  and  8  ft.  rise.  The  arch  rings  were 


ARCH  AND   GIRDER  BRIDGES.  399 

reinforced  with  4-in.,  6-lb.  channels  bent  to  a  radius  of  70  ft. 
and  spaced  1.9  ft.  c.  to  c.  The  contract  price  of  the  bridge  was 
$19,900. 

The  concrete  was  made  of  Portland  cement  and  a  natural 
mixture  of  sand  and  gravel  in  the  proportions  of  1-8  for  the 
foundations,  1-6  for  arches  and  spandrel  walls  and  1-4  for  the 
parapet  wall.  The  proportions  were  determined  by  measure ; 
the  wagon  boxes  being  built  to  hold  a  cubic  yard  of  sand  and 
gravel.  A  sack  of  cement  was  taken  as  I  cu.  ft.  For  founda- 
tions the  pit  mixture  was  used  without  screening ;  stones  over 
4  ins.  in  diameter  being  thrown  out  at  the  pit  or  on  the  mixing 
board.  For  the  arches  and  spandrel  walls  the  gravel  was 
passed  over  a  2-in.  mesh  screen  on  the  wagon  box.  The  aggre- 
gate for  the  parapet  walls  was  screened  to  I  in.  largest  diam- 
eter. The  concrete  was  mixed  in  a  McKelvey  continuous 
mixer  which  turned  the  material  eight  times.  The  mode  of 
procedure  was  as  follows:  The  gravel  was  loaded  upon 
wagons  in  the  pit  and  hauled  to  a  platform  at  the  intake  of  the 
mixer.  Half  of  the  cement  required  in  the  concrete  was  then 
spread  over  the  top  of  the  load  in  the  wagon  box  and  the 
whole  was  dumped  through  the  bottom  of  the  wagon  box  onto 
the  platform  and  spread  with  shovels.  The  remainder  of  the 
cement  was  spread  over  the  mixture  and  the  whole  was  shov- 
eled by  one  man  to  a  second  man  who  shoveled  it  into  the 
mixer.  Water  was  added  after  the  mixture  had  passed  about 
one-third  of  the  way  through  the  mixer.  The  mixer  delivered 
the  concrete  directly  into  wheelbarrows,  by  which  it  was  de- 
livered to  the  work.  The  concrete  was  spread  in  layers  from 
2  to  4  ins.  in  thickness  and  thoroughly  rammed  with  iron 
tampers ;  two  men  were  employed  tamping  for  each  man 
shoveling.  The  arches  were  concreted  in  three  longitudinal 
sections,  each  section  constituting  a  day's  work.  The  work 
was  done  in  1903  and  the  concrete  cost  for  mixing  and  placing : 
Labor :  Per  day*  Per  cu.  yd. 

13  men  at  $1.80 $23.40  $0.78 

Engine  and  mixer 5.00  0.17 

i  team   3.00  o.io 

I  foreman 3.00  o.io 

Totals  for  labor  $344O  $1.15 


400 


CONCRETE    CONSTRUCTION. 


Materials : 

0.65  bbl.  cement  at  $2    $1.30 

0.9    cu.  yd.  gravel  at  $0.50 0.45 

Total  for  materials $1.75 

Grand  total   $2.90 

METHODS  AND  COST  OF  CONSTRUCTING  A 
FIVE-SPAN  ARCH  BRIDGE.— This  bridge  consisted  of  five 
elliptical  arch  spans  of  40,  45,  60,  87  and  44  ft.,  carried  on  con- 
crete piers.  The  arch  rings  were  12  ins.  thick  at  the  crowns 
and  18  ins.  thick  5  ft.  from  the  centers  of  piers  and  carried  4-in. 


Fig.   159. — End  View  of  Center  for  Short  Elliptical   Arch   Spans. 

spandrel  walls;  there  were  1,000  cu.  yds.  of  concrete  in  the 
arches  and  600  cu.  yds.  in  the  piers.  Each  arch  ring  was  rein- 
forced by  a  grillage  of  longitudinal  and  transverse  rods. 

Forms  and  Centers. — Figure  159  is  an  end  view  of  the  center 
arch.  It  consists  of  a  series  of  bents,  6  ft.  c.  to  c.,  the  posts  of 
each  bent  being  5  ft.  c.  to  c.  These  posts  are  made  of  2  x  6-in. 
Washington  fir.  Upon  the  heads  of  the  posts  rest  2  x  6-in. 
stringers,  extending  from  bent  to  bent.  Resting  on  these 
stringers  are  wooden  blocks,  or  wedges,  which  support  a  series 
of  cross-stringers,  also  of  2  x  6-in.  stuff,  spaced  2  ft.  c.  to  c. 


ARCH  AND   GIRDER   BRIDGES. 


401 


On  top  of  these  cross-stringers  rest  the  sheeting  planks,  which 
are  I  x  6-in.  stuff,  dressed  on  the  upper  side,  and  bent  to  the 
curve  of  the  arch.  This  sheeting  plank  was  not  tongue  and 
grooved,  and  a  man  standing  under  it,  after  it  is  nailed  in 
place,  could  see  daylight  through  the  cracks.  It  looked  as  if 
it  would  leak  .like  a  sieve,  and  let  much  of  the  wet  concrete 


-aw 


I 


\, 


V 


Fig.  160.— Front  View  of  Center  for  Short  Elliptical  Arch  Spans. 

mortar  flow  through  the  cracks,  but,  as  a  matter  of  fact, 
scarcely  any  escapes.  Figure  160  shows  a  front  view  of  a  bent, 
and  indicates  the  manner  of  sway  bracing  it  with  I  ^  4-in. 
stuff.  Figure  161  shows  the  outer  forms  for  the  parapet  wall, 
or  concrete  hand  railing,  and  it  will  be  noted  that  the  cross- 
stringers  are  allowed  to  project  about  3  ft.  so  as  to  furnish  a 


/ 


Fig.    161.— Form   for   Parapet  Wall    for  Arch    Bridge. 

place  to  fasten  the  braces  which  hold  the  upright  studs.  The 
inner  forms  for  the  parapet  wall  are  shown  in  dotted  lines. 
They  are  not  put  in  place  until  all  the  concrete  arch  is  built. 
Then  they  are  erected  and  held  to  the  outer  forms  by  wire,  and 
are  sway  braced  to  wooden  cleats  nailed  to  the  top  surface  of 
the  concrete  arch. 


402  CONCRETE    CONSTRUCTION. 

For  the  five  spans  the  total  amount  of  lumber  in  the  centers 
was  in  round  figures  28  M.  ft.,  distributed  about  as  follows : 

Item.  Ft.  B.  M. 

1  x  6-in.  sheeting   5>6oo 

2  x  6-in.  longitudinal  stringers  2,600 

2  x  6-in.  cross  stringers 2,600 

2  x  6-in.  posts   4,000 

3  x  8-in.  sills 1,500 

i  x  4-in.  braces   .  .' 3,ooo 

Outer  forms  for  spandrel  walls 4,000 

Inner  forms  for  spandrel  walls 4,000 

Total  27,300 

The  aggregate  span  length  of  the  arches  was  276  ft.,  so  that 
a  little  less  than  100  ft.  B.  M.  of  lumber  was  used  for  centering 
per  lineal  foot  of  span.  The  superintendent  at  $5  per  day  and 
five  carpenters  at  $3.50  per  day  erected  the  five  centers  in  18 
days  at  a  cost  of  $400,  or  a  trifle  more  than  $14  per  M.  ft. 
B.  M. ;  the  cost  of  taking  down  the  centers  was  $2  per  M.  ft. 
B.  M.,  and  the  lumber  for  the  centers  cost  $24  per  M.  ft.  B.  M. 
making  a  grand  total  of  $40  per  M.  ft.  B.  M.  for  materials  and 
labor.  As  there  were  1,000  cu.  yds.  of  concrete  in  the  arches 
and  spandrels,  the  cost  of  centers  and  forms  was  $1.12  per 
cu.  yd.  This  form  lumber  was,  however,  after  taking  down, 
used  again  in  erecting  a  reinforced  concrete  building.  Assum- 
ing that  the  lumber  was  used  only  twice,  the  cost  of  centers 
and  forms  for  these  five  arches  was  less  than  80  cts.  per  cu.  yd. 
of  concrete. 

Shaping  and  Placing  Reinforcement. — The  60  and  87-ft. 
spans  were  reinforced  with  32  i*/2-in.  round  longitudinal  rods 
held  in  place  by  ^2-in.  square  transverse  rods  wired  at  the  in- 
tersections; the  reinforcement  of  the  smaller  spans  was  exactly 
the  same  except  that  i-in.  diameter  rods  were  used.  To  bend 
the  longitudinal  rods  to  curve,  planks  were  laid  on  the  ground 
roughly  to  the  curve  of  the  arch ;  the  exact  curve  was  marked 
on  these  planks  and  large  spikes  were  driven  part  way  into 
the  planks  along  this  mark.  The  end  of  a  rod  was  then 
fastened  by  spiking  it  against  the  first  projecting  spike  head 


ARCH  AND   GIRDER   BRIDGES. 


403 


and  three  men  taking  hold  of  the  opposite  end  and  walking 
it  around  until  the  rod  rested  against  all  the  spikes  on  the 
curve.  It  took  three  men  two  8-hour  days  to  bend  46,000  Ibs. 
of  rods.  Their  wages  were  $2.50  each  per  day,  making  the 
cost  of  bending  0.03  ct.  per  pound,  or  60  cts.  per  ton.  It  took  a 
man  5  mins.  to  wire  a  cross  rod  to  a  longitudinal  rod.  With 
wages  at  $2.50  per  day  the  cost  of  shaping  and  placing  the  re- 
inforcement per  ton  was  as  follows: 

Item.  Per  ton. 

Bending  rods $0.60 

Shearing  rods  to  lengths 0.40 

Carrying  rods  onto  bridge 0.40 

Placing  and  wiring  rods 2.35 

Total , $375 

Including  superintendence  the  labor  cost  was  practically  $4 
per  ton,  or  0.2  cts.  per  Ib.  Altogether  66,000  Ibs.  of  steel  was 
used  for  reinforcing  1,000  cu.  yds.  of  concrete,  or  66  Ibs.  per  cu. 
yd.  The  cost  of  steel  delivered  was  2  cts.  per  Ib.,  and  the  cost 
of  shaping  and  placing  it  0.2  ct.  per  Ib.,  a  total  of  2.2  cts.  per  Ib. 
or  2.2  X  66  =  $1.45  per  cu.  yd.  of  concrete. 

Mixing  and  Placing  Concrete. — A  Ransome  mixer  holding  a 
half-yard  batch  was  used.  The  mixer  was  driven  by  an  elec- 
tric motor.  The  concrete  for  the  piers  was  a  mixture  of  I  part 
Portland  cement  to  7  parts  gravel ;  for  the  arches,  the  con- 
crete was  mixed  I  to  5.  The  gravel  was  piled  near  the  mixer, 
a  snatch  team  being  used  to  assist  the  wagons  in  delivering 
the  gravel  into  a  pile  as  high  as  possible.  Run  planks  support- 
ed on  "horses"  were  laid  horizontally  from  the  mixer  to  the 
gravel,  so  that  big  wheelbarrow  loads  could  be  handled.  The 
barrows  were  loaded  with  long-handled  shovels,  and  the  men 
worked  with  great  vigor,  as  is  shown  by  the  fact  that  four 
men,  shoveling  and  wheeling,  delivered  enough  gravel  to  the 
mixer  in  8  hrs.  to  make  100  cu.  yds.  of  concrete.  We  have, 
therefore,  estimated  on  a  basis  of  six  men  instead  of  four. 
The  mixer  crew  was  organized  as  follows : 


404  CONCRETE    CONSTRUCTION. 

Per  day. 

6  men  shoveling  and  wheeling $12 

2  men  handling  cement   4 

i  man  handling  water    2 

1  man  dumping  concrete :   2 

2  men  handling  dump  cars ^ •.& 

2  men  handling  hoisting  rope   A 

4  men  spreading  and  ramming  concrete 8 

i  engineman    4 

i  foreman    5 

Fuel,  estimated  3 

Total    $48 

The  output  of  this  crew  was  100  cu.  yds.  per  day.  The  con- 
crete was  hauled  from  the  mixer  in  two  small  dump  cars,  each 
having  a  capacity  of  10  cu.  ft.  The  average  load  in  each  car 


Fig.    162. — Trestle   for   Service    Track. 

was  J4  cu-  yd.  Ordinary  mine  cars  were  used,  of  the  kind 
which  can  be  dumped  forward,  or  on  either  side.  The  cars 
were  hauled  over  tracks  having  a  gage  of  18  ins.  The  rails 
weighed  16  Ibs.  per  yard,  and  were  held  by  spikes  J4  x  2/^  ins. 
Larger  spikes  would  have  split  the  cross-ties,  which  were 
3x4  ins.  Only  one  spike  was  driven  to  hold  each  rail  to  each 
tie,  the  spikes  being  on  alternate  sides  of  the  rail  in  successive 
ties.  No  fish  plates  or  splice  bars  were  used  to  join  the  rails, 
which  considerably  simplifies  the  track  laying. 

Two  lines  of  track  were  laid  over  the  bridge.  The  tracks 
were  supported  by  light  bents,  the  cross-tie  forming  the  cap 
of  each  bent,  as  shown  in  Fig.  162.  The  bents  were  spaced 
3  ft.  apart.  There  were  two  posts  to  each  bent,  toe-nailed  at 
the  top  of  the  tie,  and  at  the  bottom  to  the  arch  sheeting 
plank.  Two  men  framed  these  crude  bents  and  laid  the  two 
rails  at  the  rate  of  150  lin.  ft.  of  track  per  day,  at  a  cost  of 


ARCH  AND   GIRDER   BRIDGES. 


405 


4  cts.  per  lin.  ft.  of  track.  As  stated,  there  were  two  tracks, 
one  on  each  side  of  the  bridge,  but  they  converged  as  they 
neared  the  concrete  mixer,  so  that  a  car  coming  from  either 
track  could  run  under  the  discharge  chute  of  the  mixer;  Fig, 
163  shows  the  arrangement  of  the  tracks  at  the  mixer.  The 
part  of  each  rail  from  A  to  B  (6  it.  long)  was  free  to  move 
by  bending  at  A,  the  rail  being  spiked  rigidly  to  the  tie  at  A, 
leaving  its  end  at  B  free  to  move.  To  move  the  end  B,  so  as 

Discharge  ^ 
\ 

A 


Mixer 


Fig.   163. — Arrangement  of  Service  Tracks  at  Mixer. 

to  switch  the  cars,  a  home-made  switch  was  improvised,  as 
shown  in  Figs.  163  and  164. 

It  will  be  remembered  that  this  bridge  was  a  series  of  five 
arches.  There  was  a  steep  grade  from  the  two  ends  of  the 
bridge  to  the  crown  of  the  center  arch.  Hence  the  two  rail- 
way tracks  ascended  on  a  steep  grade  from  the  mixer  for 


-SJidingBlock 

B 

\ 

\P/votBo/+ 


Switch 


Side    View. 

Pig.   164.— Improvised  Switch   for   Service   Cars,   General   Plan. 

about  175  ft.,  then  they  descended  rapidly  to  the  other  end  of 
the  bridge.  Hence  to  haul  the  concrete  cars  up  the  grade  by 
using  a  wire  cable,  it  was  necessary  to  anchor  a  snatch  block 
at  the  center  of  the  bridge.  This  was  done  by  erecting  a  short 


406 


CONCRETE    CONSTRUCTION. 


post,  the  top  of  which  was  about  a  foot  above  the  top  of  the 
rails.  The  post  stood  near  the  track,  and  was  guyed  by  means 
of  wires,  and  braced  by  short  inclined  struts.  To  the  top  of 
the  post  was  lashed  the  snatch  block  through  which  passed 
the  wire  rope.  Fig.  165  shows  this  post,  P.  About  i.o  ft. 
from  the  post  P ,  on  the  side  toward  the  mixer,  another  post, 
Q,  was  erected,  and  a  snatch  block  fastened  to  it.  When  the 
hoisting  engine,  which  was  set  near  the  concrete  mixer,  began 
hauling  the  car  along  the  track,  a  laborer  would  follow  the 
car.  Just  before  the  car  reached  the  post  Q,  he  would  unhook 
the  hoisting  rope  from  the  front  end  of  the  car,  then  push  the 
car  past  the  post  Q,  and  hook  the  hoisting  rope  to  the  rear  of 
the  car.  The  car  would  then  proceed  to  descend  in  the  direc- 


Fig.   165.— General  Plan   of  Rope  Haulage  System. 

tion  T,  being  always  under  the  control  of  the  wire  rope,  ex- 
cept during  the  brief  period  when  the  car  was  passing  the  post 
Q.  Each  of  the  two  cars  was  provided  with  its  own  hoisting 
rope,  and  one  engineer,  operating  a  double  drum  hoist,  handled 
the  cars.  The  hoist  was  belted  to  an  8  HP.  gasoline  engine, 
no  electric  motor  being  available  for  the  purpose. 


*  I" Poet 


Wooden 
Plug 


Fig.  166.  Fig.  167. 

Details  of  Haulage   Rope  Guides. 

Where  hauling  is  done  in  this  manner  with  wire  ropes, 'it  is 
necessary  to  support  the  ropes  by  rollers  wherever  they  would 
rub  against  obstructions.  A  cheap  roller  can  be  made  by 
taking  a  piece  of  2-in.  gas  pipe  about  a  foot  long,  and  driving 
a  wooden  plug  in  each  end  of  the  gas  pipe.  Then  bore  a  hole 
through  the  center  of  the  wooden  plugs  and  drive  a  i-in. 


ARCH  AND   GIRDER   BRIDGES.  407 

round  rod  through  the  holes,  as  shown  in  Fig.  166.  The  ends 
of  this  rod  are  shoved  into  holes  bored  into  plank  posts,  which 
thus  support  the  roller.  Where  the  rope  must  be  carried 
around  a  more  or  less  sharp  corner,  it  is  necessary  to  provide 
two  rollers,  one  horizontal  and  the  other  vertical,  as  shown 
in  Fig.  167. 

When  conveying  concrete  to  a  point  on  the  bridge  about 
300  ft.  from  the  mixer,  a  dump  car  would  make  the  round  trip 
in  3  mins.,  about  *4  mm-  of  its  time  being  occupied  in  loading 
and  another  l/\  min.  in  dumping.  One  man  always  walked 
along  with  each  car,  and  another  man  helped  pull  the  wire 
rope  back. 

Including  the  cost  of  laying  the  track  and  installing  the 
plant,  the  cost  of  mixing  and  placing  the  1,600  cu.  yds.  of 
concrete  was  only  55  cts.  per  cu.  yd.,  in  spite  of  the  high 
wages  paid.  However,  the  men  were  working  for  a  contractor 
under  a  very  good  superintendent. 

Summing  up  the  cost  of  the  concrete  in  the  arches  of  this 
bridge,  we  have: 

Per  cu.  yd. 

1.35  bbl.  cement  at  $3 $4.05 

i  cu.  yd.  gravel  at  $i i.oo 

66  Ibs.  of  steel  in  place  at  2.2  cts 1.45 

Centers  in  place   (lumber  used  once) 1.12 

Labor,  mix  and  place  concrete : 0.55 

Total $8.17 

The  cost  of  the  nails,  wire,  excavation  and  plant  rental  is 
_.ot  available,  but  could  not  be  sufficient  to  add  more  than  10 
cts.  per  cu.  yd.  under  the  conditions  that  existed  in  this  case. 
CONCRETE  RIBBED  ARCH  BRIDGE  AT  GRAND 
RAPIDS,  MICH. — The  bridge  consisted  of  seven  parabolic 
arch  ribs  of  75  ft.  clear  span  and  14  ft.  rise.  The  five  ribs 
under  the  2i-ft  roadway  were  each  24  ins.  thick,  50  ins.  deep 
at  skewbacks  and  25  ins.  deep  at  crown ;  the  two  ribs  under 
the  sidewalks  were  12  ins.  thick  and  of  the  same  depth  as  the 
main  ribs.  Each  rib  carried  columns  which  supported  the 
deck  slab.  Columns  and  ribs  were  braced  together  across- 
bridge  by  struts  and  webs.  All  structural  parts  of  the  bridge 


408 


CONCRETE    CONSTRUCTION. 


were  of  concrete  reinforced  by  corrugated  bars.  The  abut- 
ments were  hollow  boxes  with  reinforced  concrete  shells  tied 
in  by  buttresses  and  rilled  with  earth.  There  were  in  the 
bridge  including  abutments  884  cu.  yds.  of  concrete  and 
62,000  Ibs.  of  reinforcing  metal,  or  about  70  Ibs.  of  reinforcing 
metal  per  cu.  yd.  of  concrete.  Of  the  884  cu.  yds.  of  concrete 
594  cu.  yds.  were  contained  in  the  abutments  and  wing  walls 
and  290  cu.  yds.  in  the  remainder  of  the  structure.  (Fig.  168.) 


€ 


Ptets  lO^IS" 
A 


Postals" 


Posts 


Posts  IOW          A       A"  Vertical  Webs*' 

Sectional  Plan  above  Arch  Rings, 
showing  Posts,  Vertical  Webs  and  Arch  Webs. 


u..... 


|N».  New; 

Half  Longi+udinal  Section  showing  Rib"Dl!      Half   longitudinal  Section  showing  Rib"A". 
Fig.   168.— Details  of   Ribbed  Arch  Bridge. 

Centers. — The  center  for  the  arch  consisted  of  4-pile  bents 
spaced  about  12  ft.  apart  in  the  line  of  the  bridge.  The  piles 
were  12  x  12  in.  x  24  ft.  yellow  pine  and  they  were  braced  to- 
gether in  both  directions  by  2  x  lo-in.  planks.  Each  bent  car- 
ried a  3  x  12-in.  plank  cap.  Maple  folding  wedges  were  set  in 
these  caps  over  each  pile  and  on  them  rested  12  x  12-in.  trans- 


ARCH  AND   GIRDER   BRIDGES. 


409 


verse  timbers,  one  directly  over  each  bent.  These  12  x  12-in. 
transverse  timbers  carried  the  back  pieces  cut  to  the  curve  of 
the  arch.  The  back  pieces  were  2xi2-in.  plank,  two  under 
each  sidewalk  rib  and  four  under  each  main  rib  of  the  arch. 
The  back  pieces  under  each  rib  were  X-braced  together.  The 
lagging  was  made  continuous  under  the  ribs  but  only  occa- 
sional strips  were  carried  across  the  spaces  between  ribs. 
This  reduced  the  amount  of  lagging  required  but  made  work- 
ing on  the  centers  more  difficult  and  resulted  in  loss  of  tools 
from  dropping  through  the  openings.  Work  on  the  centers 
and  forms  was  tiresome  owing  both  to  the  difficulty  of  moving 
around  on  the  lagging  and  to  the  cramped  positions  in  which 
the  men  labored.  Carpenters  were  hard  to  keep  for  these 
reasons. 

Concrete. — A  1-7  bank  gravel  concrete  was  used  for  the 
abutments  and  a  1-5  bank  gravel  concrete  for  the  other  parts 
of  the  bridge.  The  concrete  was  mixed  in  a  cubical  mixer 
operated  by  electric  motor  and  located  at  one  end  of  the 
bridge.  The  mixed  concrete  was  taken  to  the  forms  in  wheel- 
barrows. The  mixture  was  of  mushy  consistency.  No  mortar 
facing  was  used,  but  the  exposed  surfaces  were  given  a  grout 
wash.  In  freezing  weather  the  gravel  and  water  were  heated 
to  a  temperature  of  about  100°  F. ;  when  work  was  stopped  at 
night  it  was  covered  with  tarred  felt,  and  was  usually  found 
steaming  the  next  morning. 

Cost  of  Work. — The  cost  data  given  here  are  based  on  fig- 
ures furnished  to  us  by  Geo.  J.  Davis,  Jr.,  who  designed  the 
bridge  and  kept  the  cost  records.  Mr.  Davis  states  that  the 
unit  costs  are  high,  because  of  the  adverse  conditions  under 
which  the  work  was  performed.  The  work  was  done  by 
day  labor  by  the  city,  the  men  were  all  new  to  this  class  of 
work,  the  weather  was  cold  and  there  was  high  water  to  inter- 
fere, and  work  was  begun  before  plans  for  the  bridge  had  been 
completed,  so  that  the  superintendent  could  not  intelligently 
plan  the  work  ahead.  Cost  keeping  was  begun  only  after  the 
work  was  well  under  way.  Many  of  the  items  of  cost  are  in- 
complete in  detail. 

The  following  were  the  wages  paid  and  the  prices  of  the 
materials  used : 


410  CONCRETE    CONSTRUCTION. 

Materials  and  Supplies : 

No.  I  hemlock  matched  per  M.  ft $20 

No.  I  hemlock  plank  per  M.  ft 17 

No.  2  Norway  pine  flooring  per  M.  ft 19 

No.  2  yellow  pine  flooring  per  M.  ft . .   20 

12  x  12-in.  x  i6-ft.  pellow  pine  per  M.  ft .  .   29 

12  x  12-in.  x  24-ft.  yellow  pine,  piling  per  M.  ft ...   27 

Maple  wedges  per  pair 50  cts. 

J/2-in.  corrugated  bars  per  Ib ,  . .  .2.615  cts. 

•}4-in.  corrugated  bars  per  Ib 2.515  cts. 

%-in.  corrugated  bars  per  Ib 2.515  cts. 

Coal  per  ton $4 

Electric  power  per  kilowatt 6  cts. 

Medusa  cement  per  bbl $1-75 

Aetna  cement  per  bbl 1.05 

Bank  gravel  per  cu.  yd 0.85 

Sand  per  cu.  yd 0.66 

Carpenters  per  day  $3  to  3.50 

Common  labor  per  day 1.75 

The  summarized  cost  of  the  whole  work,  with  such  detailed 
costs  as  the  figures  given  permit  of  computation,  was  as 
follows : 

General  Service :  Total.  Per  cu.  yd. 

Engineering    $451  $0.512 

Miscellaneous    75  0.084 

Pumping :  Total  1 10  days. 

Coal  at  $4  per  ton $210 

Machinery,  tools  and  cartage 283 

Labcr 497 


Total    $990 

This  gives  a  cost  of  $9  per  day  for  pumping. 

Excavation  :                                            Total  cost.  P.  C.  Total. 

Timber  cartage,  etc. $    375  17.6 

Tools 69  3.3 

Labor   at  $1.75 1,687  --              79-1 

Total    $2,131  100.0 


ARCH  AND   GIRDER   BRIDGES.  411 

Filling  5,711  cu.  yds.:                                Total.  Per  cu.  yd. 

Earth   $1,142  $0.20 

Labor  including  riprapping 396  0.07 


Total $1,538  $0.27 

Removing  Old  Wing  Walls :  Total. 

Labor  and  dynamite   $    346 

Tools  and  sharpening 64 

Total    $    410 

Hand  Rail,  150  ft.:  Total.  Per  lin.  ft. 

Material $    278  $1.85 

Labor    29  0.19 

Total    $    307  $2.04 

Wood  Block  Pavement,  296  sq.  yds. :  Total.  Per  sq.  yd. 

Wood  block,  etc $    695  $2.35 

Labor    57  0.19 


Total    $    752  $2.54 

Steel,  62,000  Ibs. :  Total.  Per  Ib. 

Corrugated  bars,  freight,  etc $1,498  2.41  cts. 

Plain  steel,  wire,  etc 75  0.12  cts. 

Blacksmithing,  tools  and  placing 438  0.71  cts. 

Total $2,01 1  3.24  cts. 

Concrete. 

Centering :  Total.  Per  cu.  yd. 

Lumber  and  piles $    332  $1.14 

Labor    272  0.95 


Total $    604  $2.09 

Total.  Per  cu.  yd. 

Forms    $  3,312  $  3.75 

Concrete    5>532  6-25 

Grand  total $18,113  $20.50 


412  CONCRETE    CONSTRUCTION. 

In  more  detail  the  cost  of  the  various  items  of  concrete 
work  was  as  follows  for  the  whole  structure,  including  abut- 
ments, wing  walls  and  arch  containing  884  cu.  yds.: 

Form  Construction :                                   Total.  Per  cu.  yd. 

Lumber  and  cartage  $J,547  $I-75 

Nails  and  bolts   129  0.15 

Tools    1 10  0.12 

Labor,  erecting  and  removing 1,526  1.72 

Total $3,312  $3.74 

Concrete  Construction. 
Materials : 

Aetna  cement  at  $1.05 $1,218  $i-37 

Medusa  cement  at  $1.75 499  0.56 

Sand  at  66  cts.  per  cu.  yd 37  0.04 

Gravel  at  85  cts.  per  cu.  yd 915  1.04 


Total  materials   $2,669  $3«oi 

Mixing: 

Machinery  and  supplies $    549  $0.62 

Power  at  6  cts.  per  kw 52  0.06 

Tools    22  0.02 

Labor 737  0.83 


Total  mixing  $1,360  $1.53 

Placing  concrete $  609  $0.69 

Tamping  concrete $  481  $0.54 

i 
Heating  Concrete: 

Apparatus  and  cartage .$  47  $0.05 

Fuel   96  o.i  i 

Labor    270  0.31 


Total  heating    $   413  $°47 

Grand  total   $8,844  $9.98 


ARCH  AND   GIRDER   BRIDGES. 


413 


Considering  the  abument  and  wing  wall  work,  comprising 
594  cu.  yds.,  separately,  the  cost  was  as  follows : 

Forms :  Per  cu.  yd. 

Materials  $1.20 

Labor  ; i  .09 

Total    $2.29 

Concrete : 

Materials    $2.92 

Labor    2.38 

Total $5.30 

Heating  water  and  gravel » $0.70 

Grand  total   $8.29 

Considering  the  arch  span,  comprising  290  cu.  yds.,  separ- 
ately, the  cost  was  as  follows : 

Forms :  Per  cu.  yd. 

Materials $37° 

Labor    . 3.03 


Total $6.73 

Concrete : 

Materials $3.22 

Labor    ., 3.57 

Total .$6.79 

Grand  total  $13.52 


CHAPTER    XVIII. 

METHODS    AND    COST    OF    CULVERT    CONSTRUC- 
TION. 

Culvert  work  is  generally  located  on  the  line  of  a  railway 
or  a  highway,  so  that  the  facilities  for  getting  plant  and  ma- 
terials onto  the  work  are  the  best,  and  as  culverts  are  in  most 
cases  through  embankment,  under  trestle  or  in  trench  below 
the  ground  level  the  advantage  of  gravity  is  had  in  handling 
materials  to  mixer  and  to  forms.  Ordinarily  individual  cul- 
verts are  not  long  enough  for  any  material  economy  to  be  ob- 
tained by  using  sectional  forms  unless  these  forms  are  capable 
of  being  used  on  other  jobs  which  may  occasionally  be  the 
case  where  standard  culvert  sections  have  been  adopted  by  a 
railway  or  by  a  state  highway  commission.  Various  styles  of 
sectional  forms  for  curvelinear  sections  are  given  in  Chapter 
XXI,  and  centers  suitable  for  large  arch  culverts  are  discussed 
in  Chapter  XVII.  Figure  169  shows  an  economic  form  for 
box  sections :  it  can  be  made  in  panels  or  with  continuous  lag- 
ging as  the  prospects  of  reuse  in  other  work  may  determine. 
For  curvelinear  sections  of  small  size  some  of  the  patented 
metal  forms  have  been  successfully  used. 

BOX  CULVERT  CONSTRUCTION,  C.,  B.  &  Q.  R.  R.— 

Mr.  L.  J.  Hotchkiss  gives  the  following  data.  Box  sections  of 
the  type  shown  by  Fig.  169  are  used  mostly;  they  range  in 
size  from  single  4  x  4-ft.  to  double  20  x  2O-ft.  and  triple  16  x  20- 
ft.  boxes.  These  boxes  are  more  simple  in  design  and  con- 
struction than  arches,  and  for  locations  requiring  piles  they 
are  less  expensive.  The  form  work  is  plain  and  the  space 
occupied  is  small  as  compared  with  arches,  so  that  excavation, 
sheeting  and  pumping  are  less  and  the  culvert  can  be  put 
through  an  embankment  or  under  a  tre-stle  with  less  disturb- 
ance of  the  original  structure.  Finally,  less  expensive  founda- 
tions are  required. 

414 


CULVERTS. 


For  small  jobs  where  it  does  not  pay  to  install  a  power 
mixer  a  hand  power  mixer  mounted  on  a  frame  carried  by  two 
large  wheels  has  been  found  at  least  as  efficient  as  hand  mix- 
ing; more  convenient  and  easier  on  the  men.  The  machine  is 
turned  by  a  crank  driving  a  sprocket  chain;  it  is  charged  at 
the  stock  piles  and  then  hauled  to  the  forms  to  be  discharged. 
Local  conditions  determine  the  capacity  of  power  mixer  to 
be  used.  Difficulties  in  supplying  material  or  in  taking  away 
the  concrete  may  readily  reduce  the  output  of  a  large  machine 
to  that  of  one  much  smaller,  and  the  small  machine  is 
cheaper  in  first  cost  and  in  installation  and  operation.  Where 
the  yardage  is  sufficient  to  justify  the  installation  of  equip- 
ment for  handling  the  materials  and  output  of  a  large. mixer  it 


—I0'0h 


Fig.  169.— Box  Culvert  and  Form,  C.,  B.  &  Q.  R.  R. 

is  found  preferable  to  a  small  one,  as  the  increase  in  plant 
charges  is  not  proportionately  so  great  as  the  increase  in  the 
amount  of  concrete  handled.  Again  it  may  occur  on  a  small 
job  that  the  concrete  must  be  taken  a  long  distance  from  the 
mixer,  that  a  large  batch  can  be  moved  as  quickly  and  as  easily 
as  a  small  one  and  the  time  consumed  in  doing  it  is  sufficient 
for  the  charging  and  turning  of  a  large  mixer  before  the  con- 
crete car  or  bucket  returns  to  it.  Here  a  large  mixer,  while 
it  may  stand  idle  part  of  the  time,  is  still  economic. 

The  plant  lay-outs  vary  with  the  local  conditions,  as  the 
following  will  show.  In  one  case  of  a  culvert  located  under 
a  high,  short  trestle  the  following  arrangement  of  plant  was 
employed :  A  platform  located  on  each  side  of  the  approach 


4i6  CONCRETE    CONSTRUCTION. 

embankment  about  8  ft.  below  the  ties  was  built  of  old  bridge 
timbers.  A  track  was  laid  on  each  platform  and  ran  out  over 
a  mixer  located  on  the  end  slope  of  the  embankment.  Two 
mixers,  one  for  each  platform,  were  used.  From  each  mixer 
a  track  led  out  over  the  culvert  form  and  a  track  along  the 
top  of  this  form  ran  the  full  length  of  the  culvert.  Gravel  and 
sand  were  dumped  from  cars  onto  the  side  platforms  and 
thence  shoveled  into  small  bottom  dump  cars,  which  were 
pushed  out  over  the  mixer  and  dumped  directly  into  it.  Cars 
on  the  short  tracks  from  mixers  to  culvert  form  took  the 
mixed  concrete  and  dumped  it  into  the  distributing  cars  travel- 
ing along  the  form.  The  cars  were  all  hand  pushed. 

An  entirely  different  lay-out  was  required  in  case  of  a  long 
box  culvert  located  in  a  flat  valley  some  600  ft.  from  the  track. 
A  platform  was  built  at  the  foot  of  the  embankment  with  its 
outer  edge  elevated  high  enough  to  clear  two  tracks  carrying 
5  cu.  yd.  dump  cars.  The  sand  and  gravel  was  dumped  from 
cars  onto  the  side  of  the  embankment,  running  down  onto  the 
platform  so  that  scraper  teams  moved  it  to  holes  in  the  plat- 
form where  it  fell  into  the  dump  cars.  These  cars  were  hauled 
by  cable  from  the  mixer  engine  and  dumped  at  the  foot  of  an 
inclined  platform  leading  to  a  hopper  elevated  sufficiently  to 
let  a  \Y'2  cu.  yd.  dump  car  pass  under  it.  A  team  operating  a 
drag  scraper  by  cable  moved  the  material  up  the  inclined  plat- 
form into  the  hopper,  whence  it  fell  directly  into  the  car  to 
which  cement  was  added  at  the  same  time.  The  charging  car 
was  then  pulled  by  the  mixer  engine  up  another  incline,  at  the 
top  of  which  it  dumped  into  the  mixer.  The  concrete  car  was 
hauled  up  another  incline  to  a  track  carried  on  the  forms  and 
reaching  the  full  length  of  the  culvert  work. 

The  placing  of  the  reinforcement  is  given  close  supervision. 
When  a  wet  concrete  is  used  it  is  found  necessary  to  securely 
fasten  the  bars  in  place  to  prevent  them  being  swept  out  of 
place  by  the  rush  of  the  concrete.  A  method  of  supporting  the 
invert  bars  is  shown  by  Fig.  169 ;  2  x  2-in.  stakes  are  large 
enough  and  they  need  never  be  spaced  closer  than  6  ft.  The 
longitudinal  bars  are  held  on  the  stakes  by  wire  nails  bent 
over  and  the  transverse  bars  are  wired  to  them  at  intersections 
by  stove  pipe  wire.  The  vertical  wall  bars  are  placed  by 


CULVERTS.  4x7 

thrusting  the  ends  into  the  soft  footing  concrete  and  nailing 
them  to  a  horizontal  timber  at  the  top;  the  horizontal  wall 
bars  are  wired  at  intersections  to  the  verticals.  In  the  roof 
slab  the  stakes  are  replaced  by  metal  chairs,  or  by  small 
notched  blocks  of  concrete. 

The  form  construction  is  shown  by  Fig.  169.  It  is  not  gen- 
erally made  in  panels,  since,  as  the  work  runs,  the  locations  of 
boxes  of  the  same  size  are  usually  so  far  apart  that  transporta- 
tion charges  are  greater  than  the  saving  due  to  use  a  second 
time.  No  general  rule  is  followed  in  removing  forms,  but 
they  .can  usually  be  taken  down  when  the  concrete  is  a  week 
old! 

The  boxes  are  built  in  sections  separated  by  vertical  joints, 
one  section  being  a  day's  work.  The  vertical  joints  are  plain 
butt  joints;  tongue  and  groove  joints  give  trouble  by  the 
tenons  cracking  off  in  the  planes  of  the  joints.  A  wet  mixture 
is  used  and  smooth  faces  obtained  by  spading. 

ARCH  CULVERT  COSTS,  N.  C.  &  ST.  L.  RY.— The  cost 
of  arch  culvert  construction  for  the  Nashville,  Chattanooga  & 
St.  Louis  Ry.  is  recorded  in  a  number  of  cases  as  follows : 

i8-ft.  Arch  Culvert. — Mr.  H.  M.  Jones  is  authority  for  the 
following  data:  An  i8-ft.  full-centered  arch  culvert  was  built 
by  contract,  near  Paris,  Tenn.  The  culvert  was  built  under 
a  trestle  65  ft.  high,  before  filling  in  the  trestle.  The  railway 
company  built  a  pile  foundation  to  support  a  concrete  founda- 
tion 2  ft.  thick,  and  a  concrete  paving  20  ins.  thick.  The  con- 
tractors then  built  the  culvert  which  has  a  barrel  140  ft.  long. 
No  expansion  joints  were  provided,  which  was  a  mistake  for 
cracks  have  developed  about  50  ft.  apart.  The  contractors 
were  given  a  large  quantity  of  quarry  spalls  which  they 
crushed  in  part  by  hand,  much  of  it  being  too  large  for  the 
concrete.  The  stone  was  shipped  in  drop-bottom  cars  and 
dumped  into  bins  built  on  the  ground  under  the  trestle.  The 
sand  was  shipped  in  ordinary  coal  cars,  and  dumped  or  shov- 
eled into  bins.  The  mixing  boards  were  placed  on  the  surface 
of  the  ground,  and  wheelbarrow  runways  were  built  up  as 
the  work  progressed.  The  cost  of  the  1,900  cu.  yds.  of  con- 
crete in  the  culverts  was  as  follows  per  cu.  yd. : 


4j8  CONCRETE    CONSTRUCTION. 

i.oi  bbls.  Portland  cement $2.26 

0.56  cu.  yds.  of  sand,  at  60  cts 32 

Loading  and  breaking  stone 25 

Lumber,  centers,  cement  house  and  hardware 64 

Hauling  materials 04 

Mixing  and  placing  concrete 1.17 

Carpenter  work 19 

Foreman   (100  days  at  $2.50) 13 

Superintendent  (100  days  at  $5.50) 29 

Total  per  cu.  yd $5-29 

It  will  be  seen  that  only  19  cu.  yds.  of  concrete  were  placed 
per  day  with  a  gang  that  appears  to  have  numbered  about  21 
laborers,  who  were  negroes  receiving  about  $1.10  per  day. 
This  was  the  first  work  of  its  kind  that  the  contractors  had 
done.  It  will  be  noticed  that  the  cost  of  42  cts.  per  cu.  yd.  for 
superintendence  and  foremanship  was  unnecessarily  high. 

Six  Arch  Culverts  5  ft.  to  16  ft.  Span. — All  these  arches 
were  built  under  existing  trestles,  and  in  all  cases,  except  No. 
2,  bins  were  built  on  the  ground  under  the  trestle  and  the 
materials  were  dumped  from  cars  into  the  bins,  loaded  and  de- 
livered from  the  bins  in  wheelbarrows  to  the  mixing  boards, 
and  from  the  mixing  boards  carried  in  wheelbarrows  to  place. 
Negro  laborers  were  used  in  all  cases,  except  No.  5,  and  were 
paid  90  cts.  a  day  and  their  board,  which  cost  an  additional  20 
cts. ;  they  worked  under  white  foremen  who  received  $2.50  to 
$3  a  day  and  board.  In  culvert  No.  5,  white  laborers,  at  $1.25 
without  board,  were  used.  There  were  two  carpenters  at  $2 
a  day  and  one  foreman  at  $2.50  on  this  gang,  making  the  aver- 
age wage  $1.47  each  for  all  engaged.  The  men  were  all  green 
hands,  in  consequence  of  which  the  labor  on  the  forms  in 
particular  was  excessively  high.  The  high  rate  of  daily  wages 
on  culverts  Nos.  i  and  3  was  due  to  the  use  of  some  carpenters 
along  with  the  laborers  in  mixing  concrete.  The  high  cost  of 
mixing  concrete  on  culvert  No.  2  was  due  to  the  rehandling  of 
the  materials  which  were  not  dumped  into  bins  but  onto  the 
concrete  floor  of  the  culvert  and  then  wheeled  out  and  stacked 
to  one  "Side.  The  cost  of  excavating  and  backfilling  at  the  site 
of  each  culvert  is  not  included  in  the  table,  but  it  ranged  from 
70  cts.  to  $2  per  cu.  yd.  of  concrete. 


CULVERTS.  419 

Cost  of  Six  Concrete  Culverts  on  the  N.,  C.  &  St.  L.  Ry. 
&  St.  L.  Ry. 

No.  of  culvert i             2           3           4           5          6 

Span  of  culvert 5ft.    7.66ft.  loft.     12  ft.     12  ft.     i6ft. 

Cu.  yds.  of  concrete.  210        199        354        292        406      986 
Ratio   of    cement    to 

stone    1 15.5     1 16.5     1 15.8     i  :5.8     i  :6.i     I  -.6.5 

Increase  of  concrete 

over  stone  16.0%    9.9%    6.3%   12.3%    8.3%    5.3% 

Bbls.  cement  per  cu. 

yd. 1.02       0.90       1.06       i.oi       i.oo       1.09 

Cu.  yds.  sand  per  cu. 

yd 0.43       0.49      0.44      0.46      0.46      0.47 

Cu.    yds.    stone    per 

cu.  yd 0.86      0.90      0.95       0.89      0.94      0.94 

Total      days      labor 

(inc.   foremen  and 

supt.)    702        607        784       726        768     1,994 

Av.    wages    per    day 

(inc.   foremen  and 

supt.)    $1.61     $1.33     $1.59     $1.19     $1.47     $1.46 

Cost  per  cu.  yd. — 

Cement    2.18       1.94       2.27       1.82       2.11       2.01 

Sand 0.17      0.20      0.18      0.18      0.19      0.14 

Stone    0.52       0.52      0.47      0.54      0.47      0.58 

Lumber    0.88      0.43       0.48      0.43      0.31       0.57 

Unload,   materials.  0.23       0.17      0.18      0.18      0.16      .... 

Building  forms...  1.07       0.33       0.62       0.47       0.72       0.41 

Mixing   &  placing  1.59       1.74       1.69       1.35       1.23       1.26 


Total  per  cu.  yd.  $6.64     $5.33     $5.89     $4.97     $5.19     $4.97 

i4-ft.  g-in.  Arch  Culvert. — Mr.  W.  H.  Whorley  gives  the 
following  methods  and  cost  of  constructing  a  12-ft.  full  cen- 
tered arch  culvert  204  ft.  long.  The  culvert  was  built  in  three 
sections,  separated  by  vertical  transverse  joints  to  provide  for 
expansion ;  the  end  sections  were  each  61  ft.  long  and  the 
center  section  was  70  ft.  long.  Fig.  170  is  a  cross-section  at 
the  center ;  for  the  end  sections  the  height  is  14  ft.  9  ins.,  the 
crown  thickness  is  i  ft.  9  ins.,  and  the  side  walls  at  their  bases 


420 


CONCRETE    CONSTRUCTION. 


are  5  ft.  thick.  The  concrete  was  a  1-3-6  mixture,  using  slag 
aggregate  for  part  of  the  work  and  stone  aggregate  for  a  part. 
The  culvert  was  built  underneath  a  trestle  which  was  after- 
wards filled  in. 

Miring  and  Handling  Concrete.— The  height  of  the  track 
above  the  valley  permitted  the  mixing  plant  to  be  so  laid  out 
that  all  material  was  moved  by  gravity  from  the  cars  in  which 
it  was  shipped  until  finally  placed  in  the  culvert.  Sand  and 
aggregate  were  received  in  drop  bottom  cars  and  were  un- 
loaded into  bins  in  the  trestle.  These  bins  had  hopper  bot- 
toms with  chutes  leading  to  a  wheeling  platform,  which  was 
placed  between  two  trestle  bents  and  extended  over  a  mixer 


K- 


Fig.   170.—  Section  of  Arch  Culvert,   N.,  C.  &   St.  L.  R.  R. 

placed  outside  the  trestle.  The  cement  house  was  erected 
alongside  the  trestle  at  the  wheeling  platform  level  and  a 
chute  from  an  unloading  platform  at  track  level  to  the  op- 
posite end  of  the  house  enabled  the  bags  to  be  handled  di- 
rectly from  the  car  to  the  chute  and  thence  run  by  gravity  to 
the  cement  house.  Sand  and  aggregate  were  chuted  from  the 
bins  into  wheelbarrows,  wheeled  about  23  ft.,  and  dumped  into 
a  hopper  over  the  mixer.  Water  was  pumped  by  a  gasoline 
engine  from  a  well  just  below  the  trestle  to  a  tank  on  the 
trestle,  whence  it  was  fed  to  the  mixer  by  a  flexible  connec- 
tion, a  valve  so  regulating  the  flow  that  the  necessary  amount 
was  delivered  in  the  time  required  to  mix  a  batch. 


CULVERTS.  421 

The  mixer  was  a  No.  5  Chicago  Improved  Cube  Mixer,  oper- 
ated by  a  gasoline  engine ;  a  larger  size  would  have  been  pref- 
erable since  a  batch  required  only  two-thirds  of  a  bag  of  ce- 
ment which  had  to  be  measured  which  required  the  services 
of  an  additional  man.  The  mixer  was  in  operation  194  hours 
and  mixed  7,702  batches  (1,217  cu.  yds.),  or  a  batch  every  87 
seconds,  or  6.3  cu.  yds.  per  hour.  During  the  last  ten  days  it 
mixed  a  batch  every  78  seconds  while  running.  The  best  short 
record  made  was  291  batches  in  five  .hours,  or  one  batch  every 
63  seconds,  this  being  at  the  rate  of  58  batches  equal  to  9.2 
cu.  yds.  of  concrete  in  place  per  hour,  or  nearly  1/6  cu.  yd.  per 
batch.  It  took  about  y2  minute  to  mix  the  concrete  and  about 
the  same  length  of  time  to  charge  and  discharge  the  mixer. 

To  convey  the  concrete  from  the  mixer  to  the  culvert  walls 
a  i  cu.  yd.  drop  bottom  car  was  used.  This  car  ran  on  3O-in. 
gage  tracks  carried  on  a  trestle  straddling  the  culvert  walls 
and  having  its  floor  high  enough  to  clear  the  arch.  A  track 
ran  lengthwise  of  the  trestle  over  each  culvert  wall,  and  a 
cross  track  intersecting  both  with  turntables  ran  to  the  mixer. 
Three  men  handled  the  car,  a  round  trip  to  the  extreme  end 
of  the  trestle  being  made  in  about  3  minutes.  In  the  mean- 
time the  mixer  was  discharging  into  a  small  hopper  which  un- 
loaded into  the  car  on  its  return.  One  only  of  the  three  sec- 
tions of  the  culvert  was  built  at  a  time,  both  walls  being 
brought  up  together.  After  a  point  had  been  reached  about 
2  ft.  above  the  springing  on  both  walls,  one  track  was  removed 
and  the  other  was  shifted  to  the  center  of  the  trestle. 

Forms. — There  was  used  in  the  forms  15,000  ft.  B.  M.  of 
2-in.  dressed  lagging  for  face  work,  21,000  ft.  B.  M.  rough 
lumber  for  back  work,  and  old  car  sills  for  studding.  No 
charge  was  made  for  studding  except  the  cost  of  loading,  the 
cost  of  the  remaining  lumber  was  $16  per  M.  for  dressed  and 
$12.50  per  M.  for  rough.  A  credit  of  one-third  the  cost  was 
allowed  for  the  old  material  recovered.  The  total  cost  of  the 
labor  of  erecting  the  material  in  forms,  bins  and  platforms  was 
$666.  The  work  was  done  by  a  bridge  crew  of  white  men,  the 


422  CONCRETE    CONSTRUCTION. 

average  rate  of  wages  per  man,  including  the  bridge  foreman's 
time,  being  $2.20  per  day.  In  addition  a  mason  at  $3.50  per 
day  and  a  carpenter  at  $2.25  per  day  worked  with  the  bridge 
crew  in  erecting  forms. 

Cost. — The  cost  of  the  1,217  cu-  y^s-  °f  concrete  in  the  cul- 
vert was  as  follows: 

Item.  Per  cu.  yd. 

1.08  bbls.  cement  at  $1.72 $1.85 

0.47  cu.  yd.  sand  at  30  cts 0.14 

0.25  cu.  yd.  broken  stone  at  51  cts 0.13 

0.8     cu.  yd.  slag  at  26  cts 0.21 

Lumber  in  forms, "etc 0.30 

Miscellaneous  materials 0.05 

Labor,  unloading  materials o.i  i 

Labor,  mixing  and  placing  concrete .  0.42 

Labor,  building  forms ' 0.55 

Labor,  -not  classified   0.18 

Labor,  excavating  40  cts.  per  cu.  yd 0.28 

Labor,  back  rilling  and  tearing  down  forms o.io 


Total  $4.32 

CULVERTS  FOR  NEW  CONSTRUCTION,  WABASH 

RY. — The  following  data  relate  to  culvert  work  carried  out  in 
constructing  the  Pittsburg  extension  of  the  Wabash  Ry.  in 
1903.  All  the  work  was  done  by  contract. 

Plant  I:  This  plant  was  located  on  a  hillside  with  the  crush- 
ing bins  above  the  loading  floor  or  platform  which  extended 
over  the  top  of  the  mixer,  so  that  the  crushed  stone  could  be 
drawn  directly  from  the  chutes  of  the  bins  and  wheeled  to  the 
mixer.  The  sand  was  hauled  up  an  incline  in  one-horse  carts 
and  dumped  on  this  floor,  and  was  also  wheeled  in  barrows  to 
the  mixer.  The,  proportions  used  were  4  bags  of  cement,  4 
barrows  of  sand  and  stone  dust  and  7  barrows  of  crushed 
stone.  A  %-cu.  yd.  mixer  was  used  and  it  averaged  40  cu.  yds. 
per  lo-hour  day  at  the  following  cost  for  labor : 


CULVERTS. 


423 


Item.  Per  day.     Per  cu.  yd. 

I  foreman $  3.00  $0.08 

3  men  charging  with  barrows "3--5O  O.n 

1  man  attending  engine  and  mixer 2.50  0.06 

2  men  loading  concrete  barrows 3.00  0.08 

4  men  wheeling  concrete  barrows  (100  ft.)     6.00  0.15 

4  men  ramming  concrete .  .     6.00  0.15 

4  men    wheeling     and     bedding     rubble 

stones 6.00  0.15 


Totals    $31.00  $0.78 

Assuming  ^  ton  of  coal  per  day  at  $3  per  ton,  we  have 
2  cts.  more  per  cubic  yard  for  fuel. 

Plant  II. — At  this  plant  a  Smith  mixer  was  used  with  a 
loading  floor  4  ft.  above  the  ground,  this  low  platform  being 
made  possible  by  having  a  hole  or  sump  in  which  the  skip 
receiving  the  concrete  was  set.  A  derrick  handled  the  skips 
between  the  sump  and  the  work.  The  batch  was  made  up  of 
2  bags  of  cement,  2  barrows  of  sand  and  4  barrows  of  stone. 
The  output  was  50  cu.  yds.  per  day  of  10  hours  at  the  fol- 
lowing cost : 

Item.  Per  day.       Per  cu.  yd. 

i   man   feeding  mixer $1.50  $0.03 

i   mixer  runner   2.50  0.05 

1  derrick  engineman    2.50  0.05 

2  tagmen  swinging  and  dumping 3«oo  0.06 

6  men  wheeling  materials  9.00  0.18 

2  men  tamping  concrete 3.00  0.06 

l  foreman 3.00  0.06 


Totals    $24.50  $0.49 

The  cost  of  fuel  would  add  about  3  cts.  per  cubic  yard  to 
this  amount. 

SMALL  ARCH  CULVERT  COSTS,  PENNSYLVANIA 

R.  R. — Mr.  Alex.  R.  Holliday  gives  the  following  figures  of 
cost  of  small  concrete  culvert  work  carried  out  under  his 
direction.  The  culvert  section  used  is  shown  in  Fig.  171.  This 
section  gives  a  slightly  larger  waterway  than  a  36-in.  cast  iron 


424 


CONCRETE    CONSTRUCTION. 


pipe.  Eight  culverts,  having  an  aggregate  length  of  306  ft. 
were  built,  using  a  mixture  of  Portland  cement  and  limestone 
and  screenings.  Each  culvert  had  a  small  spandrel  wall  at 
each  end. 

The  work  was  done  by  a  gang  of  six  men,  receiving  the 
following  ,  wages : 

Foreman,  cents  per  hour 27.5 

Assistant      "         "         "    17.5 

Laborers      "        "        "    15.0 

Teams  "        "        "    35.0 

The  materials  were  hauled  about  i  mile  from  railway  to  site 
of  work.  Cement,  including  freight  and  haulage,  cost  $1.97 
per  barrel.  Limestone  and  screenings  cost  50  cts.  per  cu.  yd. 
f.  o.  b.  at  quarry.  No  freight  charges  are  included  in  cost  of 
any  of  the  materials  except  cement.  The  cost  of  the  306  ft.  of 
culvert  was  as  follows : 


Per  lin.  ft. 

Per  cu.  yd. 

$145 

$3-35 

0.25 

0.60 

I.OI 

2.34 

0.04 

0.09 

3'0'  —* 
Fig.  171.— Small  Culverts,  Pennsylvania  R.  R. 

Item.  Total. 

Labor    $443.14 

Stone  and  screenings 78.50 

Cement 3°7-53 

Forms 1 2.00 

Total    $841.17  $2.75  $6.38 

26-FT  SPAN  ARCH  CULVERT.— The  culvert  was  62  ft. 
long  and  26-ft.  span  and  was  built  of  1-8  and  i-io  concrete 
mixed  by  hand.  The  wages  paid  were:  General  foreman, 
40  cts.  per  hour;  foreman,  25  cts.  per  hour;  carpenters,  22^ 
to  25  cts.  per  hour,  and  laborers,  15  cts.  per  hour.  The  cost 
of  the  concrete  in  place,  exclusive  of  excavation  but  including 
wing  walls  and  parapet,  was  as  follows : 


CULVERTS.  425 

Per  cu.  yd. 

0.96  bbl.  cement,  at  $1.60 $1-535 

1.03  tons  coarse  gravel,  at  $0.19 °-I95 

0.40  tons  fine  gravel,  at  $0.21 0.085 

0.32  tons  sand,  at  $0.36 0.115 

Tools,  etc 0.078 

Lumber  for  forms  and  centers 0.430 

Carpenter  work  on  forms  (23  cts.  hr.) 0.280 

Carpenter  work  platforms  and  buildings 0.050 

Preparing  site  and  cleaning  up 0.210 

Changing  trestle   0.085 

Handling  materials  0.037 

Mixing  and  laying,  av.  15^  cts.  per  hr 1.440 

Total  per  cu.  yd $4-54O 

There  were  1,493  cu.  yds.  of  concrete  in  the  work.  The  ex- 
cavation- cost  $463  and  the  total  cost  was  $7,243. 

COST  OF  RAILWAY  CULVERT.— The  culvert  was  for  a 
single  track  railway  and  contained  113  cu.  yds.  of  concrete 
and  required  36  cu.  yds.  of  excavation.  The  figures  are  given 
by  C.  C.  Williams  as  follows: 

Cost  of  Material. 
Kind  and  Amount  of  Material.          Unit  Price. 

Stone,   113.2  tons $  .70 

Sand,  46.8  yds 55 

Cement,  137  bbls 85 

Total ' $221.43 

Lumber 52-5° 

Rail  and  bolts    36.60 

Total $  89.10 

Excavation. 

Labor,  189  hours  at  .15 $  28.35 

Foreman,  60  hours  at  .30 18.00 

Total  .  $  46.35 


426  CONCRETE    CONSTRUCTION. 

Concrete. 

Labor,  683  hours  at  .15 $102.45 

Foreman,  130  hours  at  .30 39-QO 


Total    $14145 

Forms. 

Carpenters,  313  hours  at  .225 '.  .$  70.42 

Labor,  30  hours  at  .15 4.50 

Total    $  74.92 

Handling  Materials. 

Moving  material,  245  hours  at  .15 $  36.75 

Unloading  material,  95  hours  at  .15 14.25 

Foreman,  20  hours  at  .30 6.00 


Total   . $  57.00 

Superintendence   and   Office. 

Superintendent,  6  hours  at  .50 „ .$     3.00 

Office    ,  10.00 


Total    $  13.00 

Grand  total $643.25 

Proportional  Costs. 

Per  cent. 

Cost  of  Total 

Per  Yard         Cost  of 
Item.  Cost.  Concrete.       Concrete. 

Concrete  material    $221.43  $1.96  37.1 

Laying  concrete   .........  141.45  1.25  23.6 

Lumber   52-5o  46  08.7 

Rail  and  bolts 36.60  .32  06.1 

Building  forms 74-92  -67  13.3 

Handling  material 56.90  .50  09.0 

Superintendent  and  office.  13.00  .12  02.2 


Total  ; ,  $5.28  loo.oo 

Excavation 46.35  1.28 


Total    ..$643-i5 


CULVERTS. 


427 


Contractor's  Receipts. 

113  yds.  concrete  at  $5.95 $672.35 

36  yds.  excavation  at  .30 „ 10.80 


Total $683.15 


Total  cost 643.15. 


Profit,  5.9%  of  contract  price .$  40.00 

I2-FT.  CULVERT,  KALAMAZOO,  MICH.— A  portion 
1, 080  ft.  long  of  a  new  channel  built  in  1902-3  for  a  small 
stream  flowing  through  the  city  of  Kalamazoo,  Mich.,  was 
constructed  as  an  arch  culvert  of  the  form  shown  by  Fig.  172. 
The  concrete  section  is  reinforced  on  the  lines  indicated  by 


Fig.   172. — Cross-Section   of  Culvert  at  Kalamazoo,   Mich. 

a  double  layer  of  woven  steel  wire  fabric.    The  concrete  was 
approximately  a  I  cement,  6  sand  and  gravel  mixture. 

The  centers  were  built  in  sections  izl/>  ft.  long  of  the  form 
and  construction  shown  by  Fig.  173,  and  a  sufficient  number 
was  provided  to  lay  twelve  sections  of  invert  and  six  sections 
of  arch.  The  arch  centers  were  arranged  to  be  uncoupled  at 
the  crown ;  this  with  the  hinges  at  the  quarter  points  per- 
mitted the  two  halves  to  be  separated  and  each  half  to  be 
folded  so  that  it  could  be  carried  from  the  rear  of  the  work 
through  the  forms  still  in  place  and  erected  again  for  new 
work.  When  in  place  the  center  ribs  rested  on  the  side  forms 
which  set  on  the  invert  concrete  and  are  braced  apart  by  the 
hinged  cross-strut.  This  cross-strut  was  the  key  that  bound 


428 


CONCRETE    CONSTRUCTION. 


the  whole  structure  together ;  the  method  of  removing  this 
key  is  indicated  by  Fig.  174.  From  his  experience  with  these 
centers  the  engineer  of  fehe  work,  Mr.  Geo.  S.  Pierson. 
remarks : 

"In  work  of  this  kind  it  is  very  important  to  have  the.  cen- 
tering absolutely  rigid -so  it  will  not  spring  when  concrete  is 
being  tamped  against  it  and  thus  weaken  the  cohesion  of  the 


Cnd  Elevarion  Side  ElevoTion 

Fig.  173,— Center  for  Culvert  at  Kalamazoo,  Mich. 

concrete.  It  is  also  important  to  have  the  arrangement  such 
that  all  the  centering  can  be  removed  without  straining  or 
jarring  the  fresh  concrete.  The  centers  were  generally  re- 
moved in  about  three  or  four  days  after  the  concrete  arch 
was  in  place." 

The  invert  concrete  was  brought  to  form  by  means  of  tem- 
plates, Fig.  173,  and  straight  edges.  The  side  forms  were  then 
placed  and  braced  apart  by  the  struts  and  concreting  con- 


Hinge  ENO  NEWS 

Fig.  174. — Hinged  Cross  Strut  for  Center  for  Culvert  at  Kalamazoo,  Mich. 

tinned  to  the  skewback  plane  indicated  in  Fig.  173.  The  arch 
form  was  then  placed ;  it  rested  at  the  edges  on  the  side  forms 
and  was  further  supported  by  center  posts  bearing  on  boards 
laid  on  the  bottom  of  the  invert.  A  template,  Fig.  175,  was 
used  to  get  the  proper  thickness  and  form  of  arch  ring.  Out- 
side forms  were  used  to  confine  the  concrete  at  the  haunches 
but  nearer  the  crown  they  were  not  required. 


CULVERTS. 


429 


Much  of  the  work  was  done  when  the  thermometer, 
during  working  hours,  ranged  from  12°  to  25°  above  zero. 
When  the  temperature  was  below  freezing,  hot  water  was 
used  in  mixing  the  concrete  and  on  a  few  of  the  coldest  days 
salt  was  dissolved  in  the  water.  In  addition  each  section  of 
the  work  was  covered  with  oiled  canvas  as  soon  as  com- 
pleted, and  the  conduit  was  kept  closed  so  far  as  was  prac- 
ticable to  retain  the  heat.  Concreting  was  never  stopped  on 
account  of  cold  weather. 

Account  was  kept  of  the  cost  of  all  work,  and  the  figures 
obtained  are  given  in  the  following  fables : 


Fig.   175.—  Templet   for  Arch  Ring  for   Culvert  at   Kalamazoo,   Mich. 

Labor  Force,  Materials  Used  and  Progress  of  Work. 
Average  progress  per  day  in  feet.  ...  ......  .  .  .  .  ......   18.6 

Greatest  number  of  feet  laid  in  one  day  .............   28 

Average    number    of    laborers    per    day    mixing    and 
wheeling    ........................................ 

Average  number  of  laborers  per  day  placing  concrete.  . 
Average  number  of  laborers  per  day  setting  up  forms.  . 
Cubic  yards  of  concrete  mixed  and  wheeled  per  day  per 


10.04 
5 
4.57 


man 


Cubic  yards  of  concrete  placed  per  day  per  man  .......  .'  3.54 

Cubic  yards  of  concrete  per  lin.  ft  .....................  0.95 

Barrels  of  cement  per  lin.  ft  ..........................  1.18 

Barrels  of  cement  per  cu.  yd  ................  .  .........  1.24 

Proportion  of  cement  to  sand  and  gravel  ..............  1-6 


430  CONCRETE    CONSTRUCTION. 

Itemized  Cost  per  Lineal  Foot. 

Sand  and  gravel $0.42 

Cement   " , 2.44 

Mixing  and  wheeling  concrete  . . 0.98 

Labor  placing  concrete   0.47 

Forms   and   templates .  . . 0.30 

Metal  fabric r • 0.39 

Setting  up  forms    0.43 

Finishing    w 0.09 

Tools,  general  and  superintendence 0.43 


Total  per  lineal  foot $5-95 

The  cost  per  cubic  yard  was  thus  $6.26.  Wages  were  $1.75 
per  day. 

METHOD  AND  COST  OF  MOLDING  CULVERT 
PIPE,  CHICAGO  &  ILLINOIS  WESTERN  R.  R.— During 
1906,  the  Chicago  &  Illinois  Western  R.  R.,  Mr.  O.  P.  Cham- 
berlain, Chief  Engineer,  built  a  number  of  culverts  of  concrete 
pipe  with  an  interior  diameter  of  4  ft.,  and  6-in.  shells.  Fig. 
176  shows  the  forms  in  which  the  pipe  was  molded.  Both 
forms  are  of  ordinary  wooden  tank  construcion.  The  inner 
form  has  one  wedge-shaped  loose  stave  which  is  withdrawn 
after  the  concrete  has  set  for  about  20  hours,  thus  collapsing 
the  inner  form  and  allowing  it  to  be  removed.  The  outer 
form  is  built  in  two  pieces  with  2  x  ^g-in.  semicircular  iron 
hoops  on  the  outside,  the  hoops  having  loops  at  the  ends.  The 
staves  are  fastened  to  the  hoops  by  wood  screws  1^4  ins.  long 
driven  from  the  outside  of  the  hoop.  When  the  two  sides  of 
the  outer  form  are  in  position,  the  loops  on  one  side  come  into 
position  just  above  the  loops  on  the  other  side,  and  four  ^-in. 
steel  pins  are  inserted  in  the  loops  to  hold  the  two  sides  to- 
gether while  the  form  is  being  filled  with  concrete  and  while 
the  concrete  is  setting.  After  the  inner  form  has  been  re- 
moved, the  two  pins  in  the  same  vertical  line  are  removed 
and  the  form  opened  horizontally  on  the  hinges  formed  by  the 
loops  and  pins  on  the  opposite  side.  The  inner  and  outer 
forms  are  then  ready  to  be  set  up  for  building  another  pipe. 


CULVERTS. 


431 


The  concrete  used  in  manufacturing  these  pipes  was  com- 
posed of  American  Portland  cement,  limestone  screenings  and 
crushed  limestone  that  has  passed  through  a  y^-'m.  diameter 
screen  after  everything  that  would  pass  through  a  *^-in.  diam- 
eter screen  had  been  removed.  The  concrete  was  mixed  in 
the  proportions  of  one  part  cement  to  three  and  one-half  parts 
each  of  screenings  and  crushed  stone.  All  work  except  the 
building  of  the  forms  was  performed  by  common  laborers.  In 


|| 

JIL 

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J 

T 

III 

1 

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i 

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1 

JT.7 

t' 

li 
1 

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Mi 

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t  - 

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I  ? 

..  -li*. 

,i 

t 

i*^      . 

Ti 

Elevation  of  Outer  Form* 

Loose^dge          section  of  Inner  Forrru, 
vST^rx-^. 

Section^ 


Fig.  176.—  Form  for  Molding  Culvert  Pipe. 

his  experimental  work  Mr.  Chamberlain  used  two  laborers, 
one  of  whom  set  the  forms,  and  rilled  them  and  the  other  of 
whom  mixed  the  concrete.  The  pipes  were  left  in  the  forms 
till  the  morning  of  the  day  after  molding.  The  two  laborers 
removed  the  forms  filled  the  day  before,  the  first  thing  in  the 
morning,  and  proceeded  to  refill  them.  The  average  time 
the  concrete  was  allowed  to  set  before  the  forms  were  removed 
was  16  hours.  Mr.  Chamberlain  believes  that  with  three  men 


432 


CONCRETE    CONSTRUCTION. 


and  six  forms  the  whole  six  forms  could  be  removed  and 
refilled  daily.  Based  on  the  use  of  only  two  forms  with  two 
laborers  removing  and  refilling  them  each  day,  and  on  the  as- 
sumption that  a  single  set  of  forms  costing  $40  can  be  used 
only  50  times  before  being  replaced,  Mr.  Chamberlain  esti- 
mates the  cost  of  molding  4-ft.  pipes  as  follows: 

2  per  cent,  of  $40  for  forms $0.80 

i.i  cu.  yds.  stone  and  screenings  at  $1.85 ^  .  2.04 

0.8  bbls.  cement  at  $2.10 1.68 

10  hours'  labor  at  28  cts..  .......  2.80 


Total  per  pipe $7-32 

This  gives  a  cost  of  $1.83  per  lineal  foot  of  pipe  or  prac- 
tically $7  per  cu.  yd.  of  concrete.  The  pipe  actually  molded 
cost  $2.50  per  lin  ft.,  or  $9.62  per  cu.  yd.  of  concrete,  owing  to 
the  small  scale  on  which  the  work  was  carried  on — the  labor- 
ers were  not  kept  steadily  at  work. 

The  pipes  were  built  under  a  derrick  and  loaded  by  means 
of  the  derrick  upon  flat  cars  for  transportation.  At  the  culvert 
site  they  were  unloaded  and  put  in  by  an  ordinary  section 
gang  with  no  appliances  other  than  skids  to  remove  the  pipes 
from  the  cars.  As  each  four-foot  section  of  this  pipe  weighs 
about  two  tons,  it  was  not  deemed  expedient  to  build  sections 
of  a  greater  length  than  4  ft.,  to  be  unloaded  and  placed  by 
hand.  On  a  trunk  line,  however,  where  a  derrick  car  is  avail- 
able for  unloading  and  placing  the  pipes,  there  is  no  reason 
why  they  should  not  be  built  in  6  or  8-ft.  sections. 


CHAPTER   XIX. 

METHODS  AND  COST  OF  REINFORCED  CONCRETE 
BUILDING  CONSTRUCTION. 

If  we  set  aside  concrete  block  construction,  virtually  all 
concrete  used  in  building  construction  is  reinforced;  plain 
monolithic  or  mass  concrete  now,  as  in  the  past,  is  one  of  the 
secondary  building  materials.  It  is  reinforced  concrete  build- 
ing construction  that  is  discussed  in  this  chapter.  In  no  class 
of  concrete  work  is  the  contractor's  responsibility  for  the 
successful  outcome  of  the  work  greater  than  in  reinforced 
concrete  building  construction.  No  degree  of  excellence  in 
design  can  make  up  for  incompetent,  careless  or  dishonest 
work  in  construction.  This  is  true  not  merely  in  the  general 
way  that  it  is  true  of  all  engineering -construction — it  is  true 
in  a  special  way  peculiar  to  the  material.  Except  for  the  rein- 
forcing steel,  the  contractor  for  concrete  building  work  has  no 
guarantee  of  the  quality  of  any  element  of  his  work  except 
his  own  faithful  care  in  performing  every  task  that  combines 
to  produce  that  element.  The  quality  of  his  concrete  depends 
upon  the  care  with  which  he  has  chosen  his  cement,  sand  and 
stone  and  on  the  perfection  with  which  he  has  incorporated 
them  into  a  homogeneous  mixture.  The  quality  of  his  beam 
or  column,  then,  depends  upon  the  care  with  which  the  con- 
crete is  placed  in  position  with  the  reinforcement  and  with 
which  the  supporting  forms  are  maintained  until  the  member 
is  amply  strong  to  do  without  support.  There  is  no  certainty 
of  any  detail  except  the  certainty  that  is  had  by  performing 
every  part  of  the  work  as  experience  has  taught  that  it  should 
be  performed  if  perfect  results  are  to  be  attained.  We  have 
dwelt  thus  emphatically  on  the  responsibility  in  concrete 
building  work  of  the  contractor  for  the  reason  that  in  the 
past  it  has  been  upon  the  contractor  that  the  burden  of  failure 
has  been  generally  shifted 

433 


434  CONCRETE    CONSTRUCTION, 

The  construction  work  of  buildings  is  divided  into  (i)  con- 
struction, erection  and  removal  of  forms;  (2)  fabrication  and 
placing  of  reinforcement ;  (3)  mixing,  transporting  and  plac- 
ing concrete. 

CONSTRUCTION,    ERECTION    AND    REMOVAL    OF 

FORMS. 

The  stereotyped  text-book  statement  that  forms  must  be 
true  to  dimensions  and  shape  and  rigid  enough  in  construction 
to  maintain  this  condition  under  all  loads  that  they  have  to 
sustain  mentions  only  one  of  the  factors  that  the  constructing 
engineer  or  the  contractor  has  to  keep  in  mind  in  designing 
such  forms.  His  design  must  be  made  true  and  rigid  at  the 
least  possible  cost  for  first  construction  of  lumber  and  car- 
penter work ;  it  must  be  made  with  the  plan  in  mind  of  using 
either 'the  same  forms  as  a  whole  or  the  same  form  material 
several  times  in  one  structure;  it  must  be  made  with  a  view 
to  convenience  in  taking  down,  carrying  and  re-erecting  the 
forms  the  second  or  third  time ;  and  it  must  be.  made  with  the 
object  in  sight  of  securing  the  greatest  salvage  value  either  in 
forms  fit  for  use  again  or  in  form  lumber  that  can  be  sold  or 
worked  up  for  other  purposes. 

The  general  conditions  governing  the  computation  and 
design  of  economic  form  work  are  discussed  in  Chapter  IX. 

COLUMN  FORMS. — Concrete  columns  are  usually  square 
or  rectangular  in  section,  with,  commonly,  chamfered  or  bev- 
eled corners.  The  popularity  of  these  sections  is  due  very 
largely  to  the  simplicity  of  the  forms  required.  When  hooped 
reinforcement  is  used,  the  column  section  is  always  circular  or 
polygonal.  Hollow  sections,  T-section  and  channel  sections 
are  rarely  employed  and  then  only  for  wall  columns. 

Column  forms  should  be  made  in  units  which  can  readily  be 
assembled,  taken  apart  and  re-assembled.  The  number,  ar- 
rangement and  size  of  the  units  are  determined  by  the  shape 
and  size  of  the  column  and  the  means  adopted  for  handling 
the  forms.  For  square  or  rectangular  columns  there  wrill  be 
usually  four  units  of  lagging,  one  for  each  side,  plus  the  num- 
ber of  clamps  or  yokes  used  to  bind  the  sides  together.  Yokes 
or  clamps  will  seldom  be  spaced  over  3  ft.  apart  unless  very 
heavy  lagging  is  used;  2  ft.  spacing  for  yokes  is  common. 


REINFORCED    CONCRETE    BUILDINGS. 


435 


For  circular  columns  two  units  of  lagging  are  necessary  and 
this  is  the  number  commonly  used ;  the  yokes  or  hoops  are 
spaced  about  as  for  rectangular  columns.  Metal  forms  can  be 
used  to  good  advantage  for  cylindrical  columns.  Forms  for 
polygonal  columns  are  difficult  to  construct  in  convenient 
units.  Forms  built  complete  a  full  story  high  and  concreted 
from  the  top  are  essential  where  wet  and  sloppy  concretes  are 
used.  In  Europe,  where  comparatively  dry  concretes  are 
employed  and  where  the  reinforcement  is  commonly  placed  a 
piece  at  a  time  as  concreting  progresses,  three  sides  of  a 
rectangular  form  are  erected  full  height  and  the  fourth  side  is 
built  up  as  the  concrete  and  metal  are  placed.  This  construc- 
tion is  now  less  common,  even  abroad,  than  it  was,  since 
wetter  mixtures  are  coming  to  be  approved  by  European  en- 


Fig.  177. — Form  for  Rectangular  Column  for  Factory  Building,  Cincinnati,  O. 

gineers  to  a  greater  extent  now  than  formerly.  It  is  a  time 
consuming  method  and  writh  wet  mixtures  it  has  nothing  to 
recommend  it.  For  lagging  i%  and  2-in.  plank  are  commonly 
used ;  with  yokes  spaced  2  ft.  apart  the  lighter  plank  is  amply 
strong  and  reduces  the  weight  of  the  units  to  be  handled  as 
well  as  the  amount  of  form  lumber  required. 

Column  forms  should  always  be  constructed  with  an  open- 
ing at  the  bottom  by  means  of  which  the  reinforcement  can  be 
adjusted  and  sawdust,  shavings  and  other  material  cleaned 
out. 

Rectangular  Columns. — The  form  shown  in  section  by  Fig. 
177  was  used  in  constructing  a  factory  building  at  Cincin- 
nati, O.  Two  2x4-in.  studs  at  each  corner  carry  the  hori- 
zontal side  lagging  boards  and  are  clamped  together  by  yokes 


436  CONCRETE    CONSTRUCTION. 

composed  of  four  hardwood  corner  saddles  connected  around 
the  form  by  a  hooked  rod  with  center  turnbuckle  on  each  side. 
No  nails  are  used  in  assemblying  the  parts ;  the  same  stud- 
ding and  yokes  serve  for  several  sizes  of  column,  the  lagging 
alone  being  changed.  The  lumber  required  for  studding  is 
5^  ft.  B.  M.  per  foot  of  column  length.  The  lumber  required 
for  lagging,  using  i  in.  boards,  would  be  2%  ft.  B.  M.  for  a 
12-in.  column,  and  ^3  ft.  B.  M.  would  be  added  for  every  2-in. 
increase  in  size  of  the  column.  About  3^  ft.  B.  M.  is  required 
for  each  set  of  four  corner  saddles.  With  the  studs  rabbeted  at 
the  mill,  the  carpenter  work  is  reduced  to  the  simple  task  of 
sawing  the  boards  and  struts  to  length.  The  form  is  taken 
down  by  simply  unscrewing  the  turnbuckles;  it  can  be  erected 
by  common  labor  in  charge  of  one  carpenter  to  attend  to  the 
plumbing  and  truing-up.  The  form  can  be  used  over  and  over 
and  for  columns  of  different  sizes  without  change  except  in 
the  length  of  the  lagging  boards. 

The  form  shown  by  Fig.  178  was  used  in  constructing  a 
nine-story  warehouse  at  St.  Paul,  Minn. ;  it  is  a  design  which 
has  become  almost  standard  with  a  number  of  large  building 
contractors.  In  this  construction  lagging  boards  the  full 
length  of  the  column  are  used  and  are  held  without  nails  by 
yokes.  The  yokes  consist  of  two  heads  of  wood  held  to- 
gether by  threaded  rods  with  nuts ;  between  the  rods  and  the 
lagging  are  struts  or  blocks  serving  both  as  spacers  and  to 
hold  the  lagging  to  plane  and  surface.  The  yoke  proper  is 
adjustable  to  the  extent  of  the  threaded  portions  of  the  tie 
rods.  It  is  to  be  noticed  that  the  lagging  boards  are  not  con- 
nected by  battens  or  cleats,  therefore,  two  or  three  widths  of 
stock  serve  for  all  ordinary  changes  in  size  of  columns  and 
carpenter  work  is  limited  to  sawing  them  to  length.  Further- 
more as  the  boards  are  full  column  length,  their  salvage  value 
when  removed  from  the  forms  is  high.  Common  laborers 
under  a  carpenter  foreman  can  assemble  and  erect  the  form. 
For  a  1 2-in.  column  and  using  3  x  4-in.  yokes  spaced  2  ft.  apart 
and  i  }4 -in.  lagging,  this  form  requires  about  12  ft.  B.  M.  of 
lumber  per  foot  length  of  column.  The  column  form  shown 
by  Fig.  226  for  the  six-story  building  described  in  a  succeed- 
ing section  differs  from  the  one  described  only  in  the  details 


OF 


REINFORCED    CONCRETE    BUILDINGS. 


437 


Wectqe 


of  the  yoke  construction.  In  place  of  the  struts  between  the 
wooden  heads  of  the  yoke  a  cleat  is  nailed  across  the  project- 
ing ends  which  has  to  be  pried  loose  every  time  the  yoke  is 
removed  and  nailed  into  place  again  every  time  the  yoke  is 
put  onto  another  form  ;  these  repeated  nailings  soon  destroy 
the  yoke  heads.  This  form  as  constructed  requires  about  8^4 
ft.  B.  M.  of  lumber  per  foot  length  of  12-in.  column,  which 
is  3^4  ft.  B.  M.  less  than  is  required  for  the  form  shown  by 

Fig.  177.    The  saving  comes  entirely 
in  the  yoke  construction. 

The  form  shown  by  Fig.  238  is  of 
the  same  general  type  as  are  the  two 
just  described,  the  chief  difference  in 
detail  being  in  the  yoke  construc- 
tion and  in  the  forming  of  the  lag- 
ging boards  into  a  panel  or  unit  for 
each  side  by  means  of  battens.  This 
panel  construction  makes  a  lagging 
unit  which  is  more  convenient  to 
handle,  but  less  convenient  to  adapt 
to  changes  in  size  of  column.  The 
salvage  value  of  the  lumber  is  also 
reduced  by  the  nailing.  Assuming 
1*4  -in.  lagging  and  a  yoke  spacing  of 
2  ft.,  to  permit  direct  comparison, 
this  form  requires  iol/2  ft.  B.  M.  of 
lumber  per  foot  length  of  12-in.  col- 
umn as  compared  with  12  ft.  B.  M. 
for  the  form  shown  by  Fig.  177  and 
8^4  ft.  B.  M.  for  the  form  shown  by 
Fig.  178.  As  actually  constructed 


f 


1 

a. 

^y^A^kVVisS^// 

J 

\  ^^S^y/yf/V^SSSSN 

, 

3"x4" 

1 

warehouse  at  St.  Paul,  Minn.  wjth  2-in.  lagging  the  formshownby 
Fig.  238  requires  about  14  ft.  B.  M.  of  lumber  per  foot  length 
of  12-in.  column. 

The  French  constructor,  Hennebique,  uses  the  column  form 
construction  shown  by  Fig.  179.  Three  sides  of  the  forms  are 
built  full  length  of  vertical  plank  and  the  fourth  is  built  up  of 
horizontal  lagging  nailed  on  a  board  at  a  time  as  concreting 
progresses.  In  place  of  rectangular  yokes,  steel  clamps  of 
special  form  are  used  to  hold  the  lagging  in  place.  To  tear 


438 


CONCRETE    CONSTRUCTION. 


down  this  form  requires  drawing  the  nails  in  the  horizontal 
lagging  and  the  knocking  loose  of  the  clamps.  The  vertical 
lagging  is  of  necessity  connected  by  battens  into  panels  to 
make  it  possible  to  hold  it  in  place  by  the  form  of  clamp  used. 
Assuming  2-in.  vertical  lagging  with  %  x  3-in.  battens  every 


Fig.  179. — Form  Used  by  Mr.   Hfennebique  for  Rectangular  Columns. 

3  ft.,  and  J^-in.  horizontal  lagging  this  form  requires  about  12 
ft.  B.  M.  of  lumber  for  every  foot  length  of  12-in.  column. 
This  form  seems  to  offer  no  particular  merits  to  American 
eyes :  there  is  practically  no  saving  in  lumber  over  forms  with 
rectangular  yokes  and  the  clamp  shown,  while  adjustable,  is 


— 

ff 

/"Horizontal  Boards  •* 

1 

Fig.  180. — Form  for  Rectangular  Column  for  a  Factory  Building,   New  York 

City. 

not  nearly  so  rigid  and  secure  a  bond  for  the  lagging  as  is  a 
good  yoke. 

The  form  shown  by  Fig.  180  is  an  extreme  example  of  nailed 
construction  throughout,  no  yokes  or  clamps  being  used.  It 
was  used  in  constructing  a  factory  building-in  New  York  City. 


REINFORCED    CONCRETE    BUILDINGS. 


439 


Horizontal  lagging  nailed  to  vertical  studs  was  used  for  all 
four  sides ;  three  sides  were  built  up  full  height  and  the  fourth 
side  was  placed  a  board  at  a  time  as  concreting  progressed. 


Fig.   181.— Form  for  T-Section  Wall  Column. 

This  form  required  7J/j  ft.  B.  M.  of  lumber  per  foot  length 
of  i2-in.  column,  which  is  probably  about  as  low  in  lumber,  as 
column  form  construction  can  be  got.  The  labor  of  tearing 


•© 


g  iM  ^^^  fj 

i  i 


fie" 


7'0*\  --- 


Fig.   182.— Form  for  Corner  Wall  Column. 

down  and  re-erecting  the  form  would  be  high  as  also  would 
the  waste  of  lumber.  Nailed  forms  of  this  type  are  rarely 
used. 


440 


CONCRETE    CONSTRUCTION. 


The  form  shown  by  Fig.  181  was  used  for  molding  T-see- 
tion  wall  columns  for  a  power  station.  It  is  noteworthy  for 
its  section  ;  because  of  the  provision  for  molding  grooves  in 
the  two  sides  to  which  the  curtain  walls  join,  and  because  of 
the  manner  in  which  three  of  the  eight  sides  were  built  up  as 
the  concreting  progressed.  The  sides  a  b  c,  d  e  and  /  g  h  were 
erected  in  full  column  units  and  the  sides  c  df  e  f  and  h  a  were 
erected  in  sections  2  ft.  high  as  concreting  progressed.  The 
yokes  were  spaced  2  ft.  apart.  Using  i^-in.  stuff  for  yokes 


C/eertcthick 


1 


j 


Fig.  183.— Core  Form  for  Hollow  Column. 

and  lagging  this  form  as  built  required  about  16  ft.  B.  M.  per 
foot  length  of  column.  Except  for  the  beveling  of  the  mold 
for  the  curtain  wall  recesses,  the  framing  is  all  plain  saw  and 
hammer  work. 

A  corner  wall  column  form  is  shown  by  Fig.  182  and  as  this 
was  an  example  of  hollow  column  work  the  section  of  the 
concrete  within  the  form  is  shown.  Forms  of  this  shape  and 
of  T-section  are  properly  classed  as  special  form  work  so  that 


REINFORCED    CONCRETE    BUILDINGS. 


441 


the  examples  given  here  are  helpful  merely  as  indicating 
general  methods  that  may  be  followed.  This  particular  form 
required  15^4  ft.  B.  M.  of  %-in.  lagging  per  foot  of  column 
length,  and,  neglecting  the  special  top  frame,  about  16  ft. 
B.  M.  of  "staging"  per  foot  to  support  the  lagging.  The  core 
forms  for  molding  the  hollow  spaces  in  the  columns  of  this 
particular  building  are  shown  in  Fig.  183.  The  cross  pieces  or 
keys  carried  on  the  ^-in.  bolts  as  pivots  are  revolved  a  quarter 
turn  to  slip  clear  of  the  slots  and  permit  the  sides  to  close  to- 
gether and  free  the  core  for  withdrawal.  In  many  cases  the 
contractor  will  find  it  preferable  to  use  thin  sheet  metal  core 
molds  or  light  wooden  cores  and  leave  them  in  place.  In  one 
case  known  to  the  authors  where  hollow  wall  columns  were 


Cl 


?:: 


Fig.  184. — Form  for  Large  Rectangular  Columns. 

used  as  hot  air  ducts  for  a  heating  system  the  duct  was  laid 
up  of  one  row  of  bricks,  encircled  by  the  column  form  and  the 
annular  space  concreted  around  the  brick  duct  as  a  core.  The, 
rare  use  of  irregular  columns  makes  form  and  core  construc- 
tion for  them  a  special  problem  requiring  special  detailed  esti- 
mates in  each  case.  The  channel  section  wall  column  form 
shown'  by  Fig.  230  is  a  case  in  point ;  here  the  form  became 
practically  a  portable  mold  for  duplicating  columns  as  many 
times  as  was  desired. 

As  an  example  of  form  work  for  very  large  columns  or 
pillars  that  shown  by  Fig.  184  is  particularly  good;  it  was 
used  for  constructing  eight  3~ft.  square  pillars  for  a  water 


442 


CONCRETE    CONSTRUCTION. 


tank  tower.  The  lagging  consists  of  four  panels  made  by 
nailing  horizontal  boards  to  vertical  studs.  The  panels  are 
clamped  together  by  rectangular  yokes  spaced  3  ft.  apart. 
There  are  nearly  27^2  ft.  B.  M.  of  lumber  per  foot  length  of 
3-ft.  column  in  this  form. 

The  form  shown  by  Fig.  185  was  used  by  Mr.  R.  W.  Max- 
ton  in  constructing  a  large  factory  building  at  St.  Louis,  Mo., 
and  is  notable  for  the  means  adopted  for  centering  the  forms 
and  for  reducing  their  lateral  dimensions  to  fit  them  for 
molding  the  decreasingly  smaller  columns  of  the  upper  floors. 


Fig.  185. — Adjustable  Form  for  Rectangular  Columns. 

To  center  the  forms  the  short  angles  A  A  are  molded  into  the 
concrete  so  as  to  project  slightly  above  the  tops  of  the  floor 
slab.  Also  the  pieces  of  wood  C  are  molded  into  the  floor 
slab.  The  form  is  set  over  the  angles  and  lined  up  truly  by 
nailing  the  blocks  B  to  the  blocks  C.  It  will  be  noticed  also 
that  the  column  mold  bears  only  at  the  four  corners  the  lag- 
ging being  cut  away  somewhat  on  each  side  so  as  to  afford  an 
opening  for  cleaning.  The  lagging  for  the  sides  of  the  col- 
umn mold  is  battened  together  to  form  four  units  or  panels 
which  are  held  together  by  iron  clamps  of  the  form  shown. 


REINFORCED    CONCRETE    BUILDINGS. 


443 


Lag  screws  are  used  everywhere  in  place  of  nails.  The 
notable  feature,  however,  is  the  piecing  out  of  the  lagging 
panels  with  i-in.  strips,  one  or  more  of  which  can  be  ripped 
off  on  each  side  to  reduce  the  size  of  the  forms  as  the  columns 
grow  smaller  toward  the  top  of  the  building. 

Polygonal  Columns, — Forms  for  polygonal  columns  require 
more  lumber  and  more  carpenter  work  and  are  less  susceptible 
of  ready  arrangement  into  units  than  forms  for  rectangular 
columns.  There  is  no  approach  to  a  uniform  practice  in  their 
construction  and  the  few  forms  shown  here  are  merely  specific 
examples. 


-  Cap 


Front 
JEJevation 


Siofe 
Elevation. 


Sect/ on  A"B 
Fig.    t86. — Form    for   Octagonal   Column    for   a    Factory   Building. 


The  form  shown  by  Fig.  186  was  used  for  interior  columns 
of  octagonal  section  with  hooped  reinforcement  for  a  factory 
building.  This  form  for  a  12-ft.  octagonal  column  24  ins. 
across  between  sides  requires  approximately  325  ft.  B.  M. 
of  lumber.  The  form  shown  by  Fig.  187  was  used  by  the 
same  engineer  in  another  building;  it  is,  as  will  be  noted,  in 
four  units  coming  apart  in  joints  at  diagonally  opposite  cor- 
ners. This  form  for  an  octagonal  column  18  in.  across  between 
sides  required  about  13  ft.  B.  M. -of  lumber  per  foot  of  col- 
umn length,  with  yokes  spaced  ^2  ft.  apart.  . 


444 


CONCRETE    CONSTRUCTION. 


The  form  shown  by  Fig.  188  was  used  in  a  large  warehouse 
at  Chicago,  111.  It  will  be  noted  from  the  dotted  lines  that  one 
yoke  clamps  the  sides  a  a,  the  next  the  sides  b  b  and  so  on. 


Fig.  187.— Form  for  Octagonal  Column  for  Factory  Building. 
This  does  away  with  triangular  blocking  to  hold  the  corner 
boards   that   is   used   in   the   form   shown   by   Fig.    187.      Six 
pairs  of  yokes  were  used  for  each  column  so  that  the  yoke 


Fig.    188. — Form   for   Octagonal   Column  for  a  Warehouse,  Chicago,  111. 

spacing  was  about  2  ft.  With  2x6-in.  yokes  and  ii/2-in  lag- 
ging a  form  for  a  column  18  ins.  between  sides  would  require 
some  17  ft.  B.  M.  per  foot  of  column  length. 


REINFORCED    CONCRETE    BUILDINGS. 


445 


Circular  Columns. — Circular  columns  have  been  most  fre- 
quently molded  in  steel  forms,  and  these  are  by  all  odds  the 
best  for  general  work.  Made  in  two  parts  of  sheet  steel  and 
in  sections  that  are  set  end  to  end  one  on  another  a  form  is 
obtained  which  is  easy  to  erect,  remove  and  transport.  Wood 
forms  for  circular  columns  are  rather  clumsy  affairs  and  are 
expensive  to  construct.  Such  a  form,  Fig.  190,  is  described  in 
the  succeeding  section ;  another  is  shown  by  Fig.  189.  This 
form  was  used  successfully  for  filling  and  encasing  steel  col- 
umns for  a  fireproof  building  in  Chicago,  111.,  and  is  a  favorite 
circular  form  construction  in  Europe.  It  is  apparent  that 
the  hooping  needs  to  be  very  heavy  and  that  the  form  is  one 
that  will  be  hard  to  handle  and  rather  expensive  to  make. 

In  several  instances,  where  hooped  reinforcement  has  been 
used,  the  hooping  has  been  wrapped  with,  or  made  of,  ex- 
panded metal  or  other  meshwork,  and  the  concrete  deposited 


Fig.  189.— Form  for  Circular  Column. 

inside  the  cylinder  thus  formed,  without  other  form  work. 
A  six-story  factory  building  in  Brooklyn,  N.  Y.,  was  built 
with  circular  interior  columns  from  28  ins.  to  12  ins.  in  diam- 
eter, reinforced  by  a  cylinder  of  No.  10  3-in.  mesh  expanded 
metal,  stiffened  lengthwise  by  four  round  rods  I  in.  in  diam- 
eter for  larger  columns  to  l/2  in.  in  diameter  for  smaller 
columns.  This  reinforcement  was  set  in  place  and  wrapped 
with  No.  24  y2-in.  mesh  metal  lath,  and  the  cylinder  was  filled 
with  concrete  and  plastered  outside.  A  moderately  dry  con- 
crete is  essential  for  such  construction. 

The  method  of  molding  shells  with  the  hooping  embedded 
described  for  the  Bush  terminal  factory  work  in  another  sec- 
tion is  another  way  of  avoiding  form  work  of  the  usual  type. 

Light  steel  forms  as  well  as  the  special  construction  noted 
must  be  supplemented  by  staging  to  hold  them  in  line  and  to 
carry  the  ends  of  the  girder  forms  that  are  ordinarily  carried 


446 


CONCRETE    CONSTRUCTION. 


by  the  column  forms.  Four  uprights  arranged  around  the  col- 
umn so  as  to  come  under  the  connecting  girders  are  com- 
monly used;  they  are  set  close  enough  to  the  column  to  hold 
the  form  plumb  by  means  of  blocks  or  wedges. 

Ornamental  Columns. — Forms  for  ornamental  columns 
call  for  special  design  and  construction.  For  many  purposes, 
such  as  porch  and  portico  work,  the  best  plan  is  to  mold  the 
columns  separately  and  erect  them  as  stone  columns  of  like 
character  are  erected.  Metal  forms  of  various  patterns  are 
made  by  firms  manufacturing  concrete  block  molds  and  can 
be  purchased  from  stock  or  made  to  order.  Where  the  column 
is  to  be  molded  in  place  form  construction  becomes  a  matter 
of  pattern  making,  the  complexity  and  cost  of  which  depends 
entirely  upon  the  architectural  form  and  ornament  to  be  re- 


Fig.  190.— Form  for  Molding  Fluted  Cylindrical  Column. 

produced.  The  molding  of  ornament  and  architectural  forms 
in  concrete  is  discussed  in  Chapter  XXIII,  and  the  two  ex- 
amples of  ornamental  column  form  work  given  here  from 
recent  work  indicate  the  task  before  the  builder. 

The  form  shown  by  Fig.  190  was  used  for  molding  in  place 
fluted  columns  used  in  a  court  house  constructed  at  Mineola, 
N.  Y.  The  lagging  in  the  form  of  staves  forms  a  24-sided 
polygon  and  is  held  in  position  by  hoops  and  yokes.  The 
molds  for  the  flutes  were  formed  by  inserting  screws  from  the 
outside  so  as  to  penetrate  the  staves  and  molding  half-round 
ribs  of  plaster  of  Paris  over  them  by  means  of  the  simple 
device  shown.  To  dismantle  the  form  the  screws  were  re- 
moved and  the  lagging  taken  do'wn  leaving  the  plaster  of 


REINFORCED    CONCRETE    BUILDINGS. 


447 


Paris  in  place  as  a  protection  to  the  thin  edges  until  the  final 
finishing  of  the  building. 

The  methods  illustrated  by  Fig.  191  were  employed  in  mold- 
ing columns  in  place  for  a  church  at  Oak  Park,  111.  The  bot- 
tom portions  of  these  columns  were  plain  square  sections 
molded  in  place  in  square  molds.  The  top  portions  were 
heavily  paneled.  The  four  corner  segments  were  cast  in  glue 
molds  backed  by  wood  with  wires  embedded  as  shown.  After 
becoming  hard  they  were  set  on  end  on  the  plain  column  and 
tied  and  braced  as  shown.  The  side  openings  were  then 
closed  by  wooden  forms  and  the  interior  space  was  filled 


Fig.  191.— Form  for  Ornamental  Column  for  Church  at  Oak  Park,  111. 

with  concrete.  The  surface  facing  for  these  columns  was 
bird's-eye  gravel  and  cement,  with  very  little  sand,  mixed 
very  dry  and  placed  and  tamped  with  the  coarse  concrete 
backing. 

SLAB  AND  GIRDER  FORMS.— Slab  and  girder  construc- 
tion for  roofs  and  floors  is  of  three  kinds:  (i)  Concrete  slab 
and  steel  beam  construction  in  place;  (2)  concrete  slab  and 
girder  construction  in  place  (3)  separately  molded  slab  and 
beam  construction.  The  third  method  of  construction  is  dis- 
tinct from  the  others  in  respect  to  form  work  as  well  as  other 
details  and  is  considered  separately  in  Chapter  XX. 


448 


CONCRETE    CONSTRUCTION. 


Slab  and  I-Beam  Floors. — Centers  for  floor  slabs  between 
steel  I-beams  are  made  by  suspending  joists  from  the  beam 
flanges  and  covering  them  with  lagging.  Frequently  the 
joists  and  lagging  are  framed  together  into  panels  of  con- 
venient size  for  carrying  and  erecting.  The  construction  is  a 
simple  one  in  either  case  where  slabs  without  haunches  or 
plain  arches  form  the  filling  between  beams.  Figure  192 

l*Cemenf  anot Sarrd \ 


i 
i 

w      O 

o; 

?» 
0 

Fig.   192.— Form   for  Arch   Slab   Between   I-Beams. 

shows  an  arch  slab  center ;  plain  hook  bolts,  with  a  nut  on  the 
lower  end,  passing  through  holes  in  the  joists  are  more  com- 
monly employed.  For  i -in. 'lagging  the  joist  spacing  is  2  ft., 
for  il/2-\r\.  lagging,  4  ft.,  and  for  2-in.  lagging,  5  ft. 

A  more  complex  centering  is  required  where  the  slab  has  to 
be    haunched    around    the    I-beams.      The    center    shown    by 
193  was  designed  by  Mr.  W.  A.  Etherton  for  the  floor 


Fig.  193.— Form  for  Hat  Slab  Floor  Between  I-Beams. 

construction  of  the  U.  S.  Postoffice  Building  erected  at  Htint- 
ington,  W.  Va.,  in  1905.  The  center  consists  essentially  of 
the  pieces  A  (2  x  4  ins.  for  spans  not  exceeding  6  ft.)  and  the 
2  x  3-in.  triggers  B,  which  rest  on  the  lower  flanges  of  the 
floor  beams  and  thus  support  the  forms.  The  trigger  is 
secured  at  one  end  to  the  piece  A  by  a  i  x  3-in.  cleat  C  and  at 
the  other  end  by  i  x  3-in.  cleats  D  on  either  side  of  A,  which 


REINFORCED    CONCRETE    BUILDINGS.  449 

serve  also  as  supports  for  the  batter  boards  E.  The  six- 
penny nail  F  is  but  partly  driven  and  it  is  to  be  drawn 
before  removing  the  forms.  When  the  supports  of  the  beams 
are  not  fire-proofed  the  cleats  D  extend  to  the  bottom  of  the 
trigger  B,  but  otherwise  one  cleat  extends  lower  to  secure  the 
cross-strip  G.  To  remove  the  forms,  draw  the  partly  driven 
nail  F;  knock  off  the  strip  G  or  loosen  it  enough  to  draw  the 
nails  in  B;  pull  the  triggers  on  one  beam,  and  the  forms  will 
drop.  If  the  soffit  board  H  is  used  it  is  necessary  first  to  re- 
move the  strip  G.  For  larger  beams  use  the  spacing  blocks  H  as 
shown;  for  smaller  beams  omit  the  trigger  B  and  extend  A  to 
rest  on  the  flange  of  the  beam,  then  to  remove  the  form  A  must 
be  cut  preferably  near  the  beam. 

No  complete  records  of  the  cosi  'of  these  forms  were  ob- 
tained, but  the  following  partial  information  is  furnished  by 
Mr.  Etherton :  "Considering  a  panel  6  ft.  span  by  19  ft  long 
on  I5~in.  I-beams,  the  lumber  consisting  of  i-in.  boards  sup- 
ported by  2  x  4-in.  cross-pieces  on  2  x  3-in.  triggers  spread  3  ft. 
on  centers,  soffit  of  beams  not  fireproofed,  it  required  one  car- 
penter five  hours  at  30  cts.  per  hour  to  complete  the  panel. 
Figuring  from  this  alone  I  should  say  that  10  cts.  per  sq.  yd. 
is  a  fair  estimate  for  carpenter  work.  In  working  over  the 
forms  for  another  floor  the  i-in.  boards  require  more  time  to 
handle  and  I  should  say  that  the  saving  in  cost  of  work 
over  the  first  floor  would  be  not  over  2  cts.  per  sq.  yd.  Two 
laborers  moved  their  scaffolding  and  took  down  the  forms 
from  three  completed  panels  of  13  sq.  yds.  each  in  one  hour. 
Smaller  panels  require  a  longer  time  per  yard.  Counting  for 
the  proper  piling  of  lumber  I  should  allow  one  hour  for  one 
man  to  take  down  the  forms  for  a  13-sq.  yd.  panel  when  condi- 
tions are  the  best.  We  contracted  with  two  laborers  to  re- 
move the  forms  from  the  third  floor  and  roof  and  pile  them  in 
good  shape  on  the  ground  just  outside  of  the  building  for  an 
amount  averaging  about  4l/2  cts.  per  sq.  yd.,  and  the  men 
made  but  small  wages  on  the  contract.  The  lumber  was  used 
on  three  floors  and  the  roof,  and  the  best  of  the  i-iri.  boards 
and  all  of  the  2  x  4-in.  and  2  x  3-in.  stuff  were  used  on  a  second 
job.  For  a  safe  estimate  based  on  the  data  secured  I  should 
figure  the  cost  of  labor  and  materials  for  a  three  or  four- 
story  building  about  as  follows: 


450 


CONCRETE    CONSTRUCTION. 


Per  sq.  yd. 

Lumber  at  $20  per  thousand 28  cts. 

Carpenter  work  at  30  cts.  per  hour 10  cts. 

Labor  tearing  down  at  15  cts.  per  hour 4  cts. 

Total   per  square   yard 42  cts. 

Figure  194  shows  an  arrangement  of  centering  between 
steel  beams  which  is  novel  in  that  it  provides  for  molding  a 
slab  with  girders.  The  form  was  used  in  building  the  roof  of 
a  locomotive  roundhouse.  This  roundhouse  was  of  the  usual 
circular  form  and  had  a  radial  width  of  80  ft.  Each  radial 
roof  girder,  which  was  an  i8-in.  I-beam  was  carried  by  an 
outside  wall  pier  and  three  I-beam  columns  encased  in  con- 
crete. The  space  between  main  roof  girders  was  spanned  by 
reinforced  concrete  girders  and  roof  slab.  The  center  illus- 


K&£ho*cr  | 

^x........ .......  ^'0*. X4 

Part    Side    Elevation.  Cross  Section. 

Fig.   194. — Form  for  Slab  and  Girder  Floor  Between  I-Beams. 

trated  was  employed  for  molding  the  concrete  girders  and  slab, 
and  carries  out  the  idea  of  making  a  stiff  and  light  center  for 
considerable  spans  of  slab  without  support  by  staging.  The 
truss  construction  of  the  frames  supporting  the  girder  box 
will  be  noted. 

Concrete  Slab  and  Girder  Floors. — The  construction  of 
forms  for  this  type  of  floor  should  be  such  that  the  slab  cen- 
ters and  the  sides  of  the  girder  molds  can  be  removed  without 
disturbing  the  bottoms  of  the  girder  molds.  This  permits  the 
beams  to  be  supported  as  long  as  desirable  and  at  the  same 
time  releases  the  greater  part  of  the  form  work  for  use  again. 
It  is  of  advantage  also  to  lay.  bare  the  concrete  as  soon  as 
possible  to  the  hardening  action  of  the  free  air.  The  slabs 
may  be  similarly  supported  by  uprights  wedged  up  against 
plank  caps;  no  very  great  amount  of  lumber  is  required  for 


REINFORCED    CONCRETE    BUILDINGS. 


451 


this  staging  and  it  gives  a  large  assurance  of  safety.  It  is  well 
also  to  give  the  girder  molds  a  camber  or  to  crown  them  to 
allow  for  settling  of  the  falsework. 

The  form  shown  by  Fig.  195  was  used  in  constructing 
girders  from  14  to  23  ft.  long  in  a  factory  building  at  Cincin- 
nati, O.  The  sides  are  separate  from  the  bottom,  being  sup- 


Fig.    195.— Girder    and    Slab    Form  for  Factory  Building,  Cincinnati,  O. 

ported  at  the  ends  by  cleats  on  the  column  form  and  at  inter- 
mediate points  by  struts  under  the  yokes.  The  floor  lagging 
is  carried  by  2  x  4-in.  stringers  supported  by  the  yokes.  Up- 
rights set  under  the  bottom  plank  keep  the  girder  supported 
after  the  sides  and  slab  centers  are  removed.  It  will  be  noted 
that  the  form  is  given  a  camber  of  i-in.  The  structural  details 


Fig.   196.— Girder  and  Beam  Forms  for  Factory  Building,  Beverly,  Mass. 

are  evident  from  the  drawing.  The  form  shows  a  method  of 
molding  a  bracket  for  wind  bracing;  a  simple  modification 
fits  it  for  molding  girders  without  brackets.  A  rough  compu- 
tation gives  10  ft.  B.  M.  of  lumber  per  lineal  foot  of  girder 
form  as  shown. 


452 


CONCRETE    CONSTRUCTION. 


The  form  construction  shown  in  Fig.  196  was  employed  in 
building  the  slab  and  girder  floors  for  the  United  Shoe  Ma- 
chinery Co.'s  factory  at  Beverly,  Mass.  In  these  buildings  the 
main  girders  cross  the  building  at  2o-ft.  intervals  and  midway 
between  the  main  girders  is  a  bridging  beam  also  reaching 
across  the  building.  Floor  beams  span  the  lo-ft.  spaces  be- 
tween bridging  beams  and  main  girders  at  intervals  of  3  and 
4  ft.  Referring  first  to  the  main  girder  form,  tall  horses  are 
set  up  at  3-ft.  intervals  and  connected  by  stringers  laid  on 
the  caps.  These  stringers  carry  a  cross  piece,  with  a  cleat 
at  each  end,  over  each  horse.  The  bottom  boards  of  the  mold 
rest  on  these  cross  pieces  and  the  side  pieces  are  set  up  be- 
tween verticals  wedged  tight  between  the  cleats.  The  beam 
molds  are  a  modification  of  the  girder  molds.  The  slab  centers 

/'x4"  Battens- 2'0*C.fvC 


Fig.   197.— Girder  and  Slab  Form  for  Concrete  Building  Work. 

consist  of  panels  just  large  enough  to  span  the  openings 
between  beams  and  girders  and  composed  of  i-in.  boards 
fastened  together  by  four  i  x  5-in.  cleats.  Except  in  attach- 
ing the  quarter  round  and  triangular  moldings  for  fillets  no 
nailing  is  necessary  in  erecting  and  taking  down  the  forms. 

The  form  construction  shown  by  Fig.  197  is  one  used  by  a 
large  firm  of  reinformed  concrete  builders.  The  slab  centers 
can  be  struck  and  the  sides  of  the  girder  mold  removed  with- 
out disturbing  the  support  for  the  bottom  of  the  beam.  This 
form  runs  quite  low  in  lumber,  requiring  for  a  9x  12-in.  beam 
box  including  posts  some  9  ft.  B.  M.  per  lineal  foot  of  box. 
The  joists  and  lagging  as  shown  require  about  2  ft.  B.  M.  per 
square  foot  of  floor  slab.  The  practice  is  to  give  these  girder 
boxes  a  camber  of  y2-in.  in  10  ft. 


REINFORCED    CONCRETE    BUILDINGS. 


453 


The  construction  shown  by  Fig.  198  is  designed  to  provide 
adjustability,  to  enable  quick  erection  and  removal  and  to  do 
away  with  all  nailing.  The  construction  is  as  follows :  Wood- 
en posts  carry  at  their  tops  steel  T-beam  cross-arms  knee 
braced  to  the  posts  by  steel  straps.  The  cross-arms  carry  the 
two  jaws  of  a  clamp,  each  consisting  of  a  vertical  plate, 
and  two  diagonal  braces,  slotted  so  as  to  slide  on  the 
T-beam.  A  cut  nail  or  other  piece  of  metal  driven  into  the 
slots  fastens  the  jaws  on  the  T-beam.  The  cross-arms  carry 
the  bottom  boards  of  the  girder  molds  and  the  vertical  plates 


,s*.m: 


1 


Fig.   198.— Girder  and   Slab  Form  for  Warehouse  at  St.  Paul,   Minn. 

of  the  jaws  support  the  side  pieces.  A  blocking  piece  slipped 
between  the  braces  carries  the  end  of  the  joist  for  the  floor 
slab  centers.  This  form  is  the  invention  of  Mr.  W.  H.  Dillon 
and  was  used  in  constructing  the  nine-story,  26oxi5O-ft. 
wholesale  hardware  store  of  Farwell,  Osman  &  Kirk  Co.,. St. 
Paul,  Minn. 

The  form  shown  by  Fig.  199  was  used  in  constructing  a 
factory  building  in  Long  Island  City,  N.  Y.,  and  it  is  given 
here  chiefly  for  the  purpose  of  exhibiting  the  unnecessary  com- 
plexity of  form  work.  Comparing  this  form  with  that  of 


454 


CONCRETE    CONSTRUCTION. 


nearly  any  of  the  preceding  designs  will  bring  out  the  point. 
The  design,  however,  was  one  of  the  earlier  ones  to  recognize 
the  advantage  of  stripping  the  slab  centers  and  the  sides  of  the 
girder  boxes  without  disturbing  the  bottom  plank  of  the 
boxes  or  the  staging.  The  drawing  shows  the  independent 
support  of  the  bottom  board  and  side  pieces  of  the  girder 
mold  on  the  transverse  caps  of  the  staging  posts.  These 
posts  are  6x8  ins.  in  section  and  are  spaced  from  6  to  8  ft. 
apart.  Briefly  described  the  bottom  board  is  a  single  plank 
from  i  to  3  ins.  thick,  to  which  the  side  pieces  are  lag-screwed 
at  the  bottom.  The  side  pieces  are  panels  composed  of  4x  %- 
in.  vertical  boards  nailed  to  top  and  bottom  2x4-in.  horizontal 
timbers.  A  third  horizontal  timber  near  the  top  serves  as  a 
seat  for  the  ends  of  the  joists  carrying  the  slab  lagging  and 
is  braced  from  the  bottom  horizontal  by  vertical  stiffeners. 


Fig.  199.— Girder  and  Slab  Form  for  Factory  Building,  New  York,  N.  Y. 

The  eldge  boards  of  the  slab  lagging  are  nailed  to  the  top 
edges  of  the  side  pieces  of  the  girder  mold  and  the  tops  of 
these  side  pieces  are  connected  across  the  trough  by  strips  of 
board;  all  the  slab  lagging  boards  except  those  at  the  edges 
of  the  girder  molds  are  laid  loose.  In  the  building  referred  to, 
after  the  floor  concrete  had  set  about  seven  days  the  joists 
carrying  the  slab  lagging  were  turned  a  quarter  over  thus 
dropping  the  slab  form  about  2  ins.  A  few  days  later  the 
joists  and  lagging  were  taken  down  and  the  side  pieces  of  the 
girder  mold  were  unscrewed  and  removed.  The  bottom  board 
and  staging  posts  were  left  in  position  about  three  weeks 
longer  and  then  dropped  about  I  in.  by  removing  fillers  from 
the  staging  post  caps.  In  another  week  the  bottom  boards'and 
staging  posts  were  taken  down.  This  construction  of  form 


REINFORCED    CONCRETE    BUILDINGS. 


455 


and  method  of  removing  it  permitted  the  concrete  to  be 
stripped  so  that  the  air  could  get  at  it  as  fast  as  it  was  safe  to 
take  the  support  from  any  part  and  at  the  same  time  kept  the 
supports  in  such  position  that  they  form  a  safety  platform  in 
case  of  collapse.  A  more  important  advantage  is  that  the  form 
timber  can  be  removed  as  fast  as  any  part  of  it  is  free  and 
used  again.  Thus  the  lagging  boards  and  joists  and  the  side 
pieces  for  the  girder  molds  were  free  for  use  again  about  every 
two  weeks  and  yet  the  main  supports  of  the  girders  were  un- 
disturbed until  they  were  fully  a  month  old. 

Other  examples  of  girder  and  slab  forms  are  shown  in  the 
succeeding  sections  describing  the  construction  of  a  six-story 
building  and  of  a  garage  constructed  at  Philadelphia,  Pa. 

Another  type  of. slab  and  girder  form  construction  that  de- 
serves brief  mention  because  of  its  variation  from  usual  prac- 
tice and  also  because  of  its  extensive  use  by  one  prominent 


I 


Fig.  200.— Collapsible  Core  Forms  for  Girder  and  Slab  Floors. 

builder  is  shown  by  Fig.  200.  Cores,  or  inverted  boxes,  with 
four  vertical  sides  and  rounded  corners,  are  set  side  by  side, 
with  ends  on  stringers  carried  by  the  column  forms,  at  inter- 
vals wide  enough  to  enable  the  beam  to  be  molded  between. 
A  plank  resting  on  cleats  on  the  sides  of  the  cores  forms  the 
bottom  of  the  beam  mold.  The  main  girders  are  molded  in 
similar  spaces  between  the  ends  of  the  cores  in  one  panel  and 
of  those  in  the  next  panel.  To  permit  the  core  to  be  loosened 
readily  it  is  hinged ;  when  in  place  spacers  inside  the  core 
keep  the  sides  from  closing.  These  are  knocked  out,  the  core 
sides  close  together  and  the  core  is  removed  for  use  in  another 
place.  Cores  similar  to  these  were  used  in  molding  the  ribbed 
floor  for  the  Bush  terminal  factory  building  described  in  a 
succeeding  section.  These  cores  are  capable  of  repeated  use 
so  that  while  they  are  somewhat  expensive  to  frame  they  give 


456 


CONCRETE    CONSTRUCTION. 


a  very  low  cost  of  form  work  when  the  beam  and  girder  spac- 
ing is-  arranged  largely  in  duplicate  from  floor  to  floor.  It  will 
ordinarily  be  cheaper  to  have  these  cores  made  to  pattern  by 
regular  woodworking  shops,  and  shipped  to  the  building  ready 
to  erect. 

WALL  FORMS. — Wall  work  in  modern  commercial  and 
manufacturing  buildings,  when  we  come  to  eliminate  windows 
and  wall  columns  and  girders,  is  confined  very  largely  to  iso- 
lated curtain  wall  panels  between  windows  and  framework. 
In  such  buildings,  therefore,  wall  forms  consist  merely  of 


Fig.  201.— Continuous  Form  for  Wall  Construction. 

wooden  panels,  one  for  each  face  of  the  wall,  constructed  to 
fit  the  spaces  to  be  walled  up.  Where  these  spaces  are  dupli- 
cated from  bay  to  bay  or  story  to  story  the  same  form  panels 
will  serve  repeatedly.  For  residences  and  other  buildings 
having  greater  proportionate  area  of  blank  wall  the  builder  has 
a  choice  between  continuous  forms  carried  by  staging  and 
movable  panel  forms. 

For  one  and  two-story  buildings,  with  the  usual  variation  in 
architectural  detail,  panel  work  and  window  work,  the  con- 
tinuous form  has  many  advantages,  and  the  superior  economy 


REINFORCED    CONCRETE    BUILDINGS. 


457 


of  movable  panels  in  retaining  and  other  plain  wall  work  is  by 
no  means  always  true  here.  One  good  type  of  continuous 
wall  form  construction  is  shown  by  Fig.  201.  The  gallows 
frames  are  spaced  about  6  ft.  apart  along  the  wall  and  con- 
nected by  horizontal  stringers  nailed  to  the  uprights  or  by 
diagonal  bracing.  Each  frame  may  be  made  up  of  6x6-in. 
posts  connected  by  2  x  4-in.  cross-struts  and  diagonals  with 
bolted  connections  so  that  the  frame  can  be  taken  down  and 
put  together  easily  and  so  that  the  bracing  can  be  removed 
as  the  wall  is  built  upward.  The  other  details  of  the  form 


[' 


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Spacer 


Fig.  202.— Sectional  Form  for  Wall  Construction. 

work  are  shown  by  the  drawing.  This  construction  leaves  a 
clear  space  for  placing  the  concrete  and  the  cross  pieces  give 
support  to  runways;  it  has  been  successfully  used  in  a  large 
amount  of  low  building  work. 

Movable  panel  forms  are  of  great  variety  in  detail  but  are 
generally  of  either  one  or -the  other  types  shown  by  Figs. 
202  to  204. 

The  form  shown  by  Fig.  202  was  used  in  constructing  a 
church  at  Oak  Park,  111.  For  the  back  of  the  wall  it  consists 
of  continuous  lagging  held  by  2x4  studs.  For  the  face 


458 


CONCRETE    CONSTRUCTION. 


ix6-in.  lagging  12  ft.  long  was  nailed  to  2x4-in.  studs  to 
form  panels.  It  will  be  noted  that  the  ends  of  the  studs  are 
scarfed  so  as  to  interlock  in  succeeding  panels.  This  construc- 
tion also  shows  a  method  of  supporting  the  reinforcing  bars 
inside  the  form. 

The  form  shown  by  Fig.  203  was  used  in  constructing  a 
large  factory  building,  and  consisted  of  two  side  pieces  or 
panels  3  ft.  high  and  16  ft.  long,  the  distance  between  wall 
columns.  For  the  first  course  these  were  seated  on  the  care- 
"fully  leveled  and  rammed  ground  and  securely  braced  by  in- 
clined or  horizontal  struts  inside  and  outside  of  the  building. 
After  the  concrete  had  set  for  three  days  the  molds  were 
loosened  and  lifted  until  the  lower  edges  were  2  ins  below 


Ties  4  apart 


Fig.   203. — Sectional   Form  for  Wall  Construction. 

the  top  of  the  concrete  and  there  they  were  held  by  horizontal 
bolts  through  their  lower  edges  and  across  the  top  of  the 
concrete  by  ties  nailed  across  their  tops  every  3  ft.  and  by 
bracing  to  the  falseworks  supporting  the  column  and  floor 
forms.  The  cross  bolts  passed  through  pasteboard  sleeves 
which  were  left  permanently  embedded  in  the  wall.  By  start- 
ing the  molds  level  and  finishing  each  course  level  with  their 
tops  no  difficulty  was  had  in  keeping  the  forms  plumb  and  to 
level  as  they  were  moved  upward.  This  type  of  form  has  to 
be  exteriorly  braced  to  staging  or  adjacent  column  forms,  etc. 
The  type  of  movable  panel  form  shown  by  Fig.  204  depends 
for  all  support  on  the  wall  alone.  The  sketch  shows  the  form 
filled  ready  to  be  shifted  upward ;  this  operation  consists  in 


REINFORCED    CONCRETE    BUILDINGS. 


459 


removing  the  bottom  bolts  and  loosening  the  top  bolts  enough 
to  premit  the  studs  to  be  slid  upward  the  full  length  of  the 
slots.  The  lagging  boards  left  free  are  then  removed  and 
placed  on  top  and  the  bolts  are  tightened,  completing  the  form 
for  another  section  of  wall. 


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Fig.  204.— Movable  Panel  Form  for  Wall  Construction. 

A  type  of  wall  form  construction  intended  to  do  away  with 
studding  and  bracing  is  illustrated  by  Figs.  205  and  206.     In 
both  cases  metal  plank  holders  are  used  in  place  of  studs,  and  , 
practically  the  only  difference  between  the  two  is  in  the  shape 


Fig.  205.— Sullivan's  Plank  Holders  for  Wall  Forms. 

and  material  of  the  holders.  The  mode  of  procedure  is  to 
work  in  horizontal  courses  one  plank  high  around  the  wall, 
removing  the  bottom  plank  and  placing  it  on  top  as  each  new 
course  is  begun  after  the  first  few  courses  have  been  laid. 


460 


CONCRETE    CONSTRUCTION. 


Using  the  arrangement  shown  by  Fig.  205  in  constructing  a 
building  100x54  ft.  in  plan  and  36  ft.  high  with  12-in.  walls, 
a  height  of  two  12  x  2-in  planks  was  all  the  form  work  that 
was  ever  necessary  at  any  one  time,  so  that  the  amount  of 
form  lumber  required  for  the  building  was  2,464  ft.  B.  M.  plus 
205  ft.  B.  M.  of  2  x  4-in.  flooring  strip,  or  altogether  2,669  ft- 
B.  M.,  or  0.24  ft.  B.  M.  per  square  foot  of  exterior  wall  surface, 
or  6l/2  ft.  B.  M.  per  cubic  yard  of  concrete.  This  same  form 
lumber  with  16  additional  plank  was  then  used  to  construct  a 
building  loox  100  ft.  x  i6ft.  high,  so  that  some  3,000  ft.  of 
form  lumber  sufficed  for  17,548  sq.  ft.  (exterior  surface)  of 
wall  or  for  617  cu.  yds.  of  concrete  in  12-in.  wall,  which  gives 
0.17  ft.  B.  M.  per  square  foot  or  4.8  ft.  B.  M.  per  cubic  yard 
of  concrete. 


Pig.  206.— Farrell's  Plank  Holders  for  Wall  Forms. 

ERECTING  FORMS.— The  organization  of  the  erecting 
gang  will  depend  very  largely  on  the  manner  in  which  the 
forms  have  been  constructed.  If  they  have  been  constructed 
in  sections  which  go  together  with  wedges  and  clamps  com- 
mon laborers  with  a  foreman  carpenter  in  charge  to  direct 
and  to  line  and  level  the  work  will  do  the  erecting,  but  if  they 
have  to  be  largely  built  in  place  carpenters  are  necessary  for 
all  the  work  except  carrying  and  handing.  There  should  be 
at  least  one  foreman  for  every  15  to  20  men  and  a  head  fore- 
man in  charge  of  all  form  work.  The  mode  of  procedure  will 
differ  for  every  job,  but  the  following  general  directions  apply 
to  all  work  in  greater  or  less  measure. 


REINFORCED    CONCRETE    BUILDINGS.  461 

Clamps,  bolts  and  wedges  and  not  nails  should  be  used 
wherever  possible  in  assembling  parts  of  forms  in  erection; 
these  devices  are  not  only  quickly  and  easily  applied  in 
erection  but  they  are  just  as  quickly  and  easily  loosened  in 
taking  down  forms  and  they  can  be  loosened  without  jarring 
the  concrete  member. 

Lining  girder  forms  and  lining  and  plumbing  column  and 
wall  forms  is  high-class  carpenter  work  and  should  be  directed 
by  competent  carpenters.  A  column  or  girder  which  is  out  of 
line  or  plumb  not  only  looks  bad  but  may  be  required  to  be 
removed  and  corrected  by  the  engineer.  The  expense  for  one 
such  correction  will  be  many  times  that  which  would  have 
been  involved  by  proper  care  in  the  first  place. 

Supports  or  staging  for  the  forms  should  be  used  freely 
and  well  braced  in  both  directions.  Uprights  should  be  set  on 
wedges  and  bear  against  a  cap  piece  and  on  a  sill  piece  to 
distribute  the  load. 

Erect,  line  and  plumb  the  column  forms  first;  then  erect, 
line  and  level  the  girder  forms  and  set  the  girder  staging,  and 
finally  erect  and  level  the  slab  centers  and  their  supports. 

Leave  the  foot  of  each  column  form  open  an  one  side  at  the 
bottom  so  that  the  column  reinforcement  can  be  adjusted  and 
connected  up  and  so  that  a  clear  view  can  be  had  through 
the  form  to  detect  any  object  that  may  have  fallen  into  the 
form  and  become  wedged ;  this  same  opening  makes  it  pos- 
sible to  clean  the  form. 

Give  the  forms  a  final  inspection  before  concreting  to  check 
line  and  level,  to  close  open  joints  and  to  tighten  up  clamps 
and  wedges.  Finally  clean  each  form  and  wet  it  down  thor- 
oughly before  placing  the  concrete — do  this  just  before  placing 
the  concrete. 

REMOVING  FORMS.— Good  judgment  and  extreme  care 
are  essential  in  removing  centers.  It  goes  without  saying 
that  forms  should  never  be  removed  until  the  concrete  has  set 
and  hardened  to  such  strength  that  it  will  sustain  its  own 
dead  weight  and  such  live  load  as  may  come  upon  it  during 
construction.  The  determination  of  this  condition  is  the  mat- 
ter that  calls  for  knowledge  and  judgment.  Some  cements 
set  and  harden  more  rapidly  than  others,  and  concrete  hard- 


462  CONCRETE    CONSTRUCTION. 

ens  more  and  more  slowly  as  the  temperatue  falls.  These  and 
other  circumstances  must  all  be  taken  into  account  in  decid- 
ing upon  the  safe  time  for  removal.  Many  large  contractors 
mold  a  cube  of  concrete  for  each  day's  work  and  leave  it  stand- 
ing on  the  finished  floor  exposed  to  the  same  conditions  as 
the  concrete  in  the  forms ;  examination  of  this  sample  block 
gives  a  line  on  the  condition  of  the  concrete  in  the  work  and 
on  the  probable  safety  of  removing  the  forms  at  any  time.  In 
all  cases  it  should  be  the  superintendent's  duty  to  determine 
when  to  remove  forms,  and  he  should  satisfy  himself  by  per- 
sonal inspection  that  the  concrete  is  in  condition  to  stand 
without  support.  It  is  also  wise  at  least  as  a  matter  of  precau- 
tion for  the  contractor  to  secure  the  engineer's  or  the  archi- 
tect's approval  before  removing  any  formwork. 

Care  in  removing  forms  is  essential  for  the  reason  that 
green  concrete  is  particularly  susceptible  to  injury  from  shock 
or  sudden  strain.  It  is  well,  therefore,  to  have  a  separate  gang 
always  doing  the  work.  These  men  will  in  a  few  days  become 
trained  under  an  experienced  foreman  so  that  they  will  not 
only  do  the  work  with  greater  safety  but  also  more  rapidly. 
This  gang  should,  furthermore,-  be  required  to  follow  a  regu- 
lar system  in  its  work;  a  system  which  may  not  be  departed 
from  without  direct  orders  from  the  superintendent.  An 
example  of  such  a  system  is  outlined  below. 

The  time  of  beginning  this  work  of  removal  shall  be  given 
by  the  superintendent.  In  warm,  dry  weather,  with  other  con- 
ditions favorable,  removal  may  be  begun  after  seven  days. 
Then  the  following  schedule  may  be  followed :  At  the  end  of 
seven  days  remove  the  sides  of  the  column  forms.  This  gives 
an  opportunity  to  determine  the  soundness  of  the  column 
casting  and  also  serves  the  further  desirable  purpose  of  baring 
the  concrete  to  the  curing  and  hardening  action  of  the  air.  At 
the  end  of  14  days  loosen  the  wedges  of  the  posts  supporting 
the  slab  centers  and  drop  these  centers  a  couple  of  inches ; 
leave  the  centers  in  this  position  for  another  day,  meanwhile 
examining  the  tops  of  the  slabs  to  note  their  condition.  Then 
remove  the  sides  of  the  beam  molds  and  the  slab  centers,  re- 
placing the  latter  with  temporary  uprights  supporting  a  plank 
bearing  against  the  underside  of  the  slab.  This  precaution  is 
often  neglected  and  with  very  little  reason  considering  the 


REINFORCED    CONCRETE    BUILDINGS.  463 

importance  of  the  safeguard  thus  secured.  Ordinarily  the 
shores  need  not  be  left  in  place  more  than  a  week,  so  that  the 
amount  of  lumber  thus  tied  up  is  small.  At  the  end  of  three 
weeks  remove  the  uprights  under  the  beam  and  girder  molds 
and  strip  the  bottom  plank.  In  this  schedule  it  is  assumed 
that  the  floor  is  free  from  any  great  load  and  that  no  unusual 
loading  is  put  upon  it ;  if  a  load  of  any  consequence  is  to  come 
on  the  floor  the  shores  and  uprights  should  be  left  in  place 
longer.  No  schedule  of  removal  can  be  blindly  followed,  and 
that  given  above  is  certain  only  when  the  conditions  are  right 
and  as  stated. 

FABRICATION  AND  PLACING  OF  REINFORCEMENT. 

The  amount  of  reinforcing  steel  used  varies  from  50  Ibs.  to 
275  Ibs.  per  cu.  yd.  of  concrete ;  the  highest  figure  will  be  had 
only  in  very  heavy  work  and  where  very  heavily  reinforced 
raft  foundations  are  employed,  and  the  lowest  only  in  one- 
story  buildings  consisting  of  walls  and  roof.  A  fair  average 
is  perhaps  150  Ibs.  per  cu.  yd.  The  cost  of  fabricating  and 
placing  reinforcement  will  run  from  l/$  ct.  to  il/2  cts.  per 
pound,  but  the  last  figure  is  exceedingly  high ;  $4  ct-  per  pound 
for  fabricating  and  placing  is  a  reasonable  labor  charge. 

Contractors  frequently  have  their  choice  whether  the  steel 
shall  be  fabricated  into  frames  and  placed  as  units  or  whether 
it  shall  be  placed  in  separate  bars.  For  girders  and  columns 
the  difference  in  cost  of  the  two  methods  is  not  so  very  great 
for  steel  in  place  when  the  fabrication  is  done  in  the  field. 
The  unit  frames  cost  considerably  more  than  separate  bars  to 
fabricate,  but  the  cost  of  handling  and  placing  them  in  the 
forms  is  materially  less;  on  an  average  the  differences  balance 
each  other.  Where  the  frames  are  made  up  in  regular  mills 
unit  frames  generally  cost  less  to  fabricate  and  place  than  do 
separate  bars.  The  use  of  unit  frames  in  wall  and  floor  slab 
reinforcement  is  generally  more  expensive  than  the  use  of  sep- 
arate bars.  The  chief  gain  that  comes  from  the  use  of  unit 
frames  is  the  gain  due  to  the  certainty  that  the  reinforcing 
bars,  stirrups,  etc.,  are  all  there  and  are  properly  spaced  and 
placed. 


464 


CONCRETE    CONSTRUCTION. 


FABRICATION. — Fabrication  includes  all  the  work  nec- 
essary to  prepare  the  reinforcement  ready  to  place  in  the 
forms.  It  amounts  to  very  little  where  separate  bar  types. of 
reinforcement  are  used.  Plain  bending  and  shearing  opera- 
tions comprise  the  whole  task.  Where  the  beam  or  column 
reinforcement  has  to  be  made  up  into  complete  frames  which 
can  be  handled  and  placed  as  units  this  task  is  more  complex 
and  considerable  apparatus  is  essential  to  rapid  and  econom- 
ical work.  For  this  reason  it  is  wise  usually  to  contract  with 
some  metal  working  shop  to  assemble  and  connect  up  the 


Fig.  207. — Rack  for  Storing  Reinforcing  Bars. 

various  units  and  to  furnish  them  ready  for  installation.  In 
many  cases  these  unit  frame  types  of  reinforcement  are  pat- 
ented and  the  proprietors  contract  to  fabricate  and  furnish 
them  complete  according  to  the  plans  of  the  engineer  or  archi- 
tect. Even  where  the  frame  construction  is  not  so  con- 
trolled it  will  be  economy  generally  to  have  the  fabrication 
done  at  regular  shops  where  the  necessary  tools  and  skilled 
workmen  are  had.  In  any  case  the  bars  should  be  ordered  cut 
to  length  at  the  mill  so  far  as  possible. 


REINFORCED    CONCRETE    BUILDINGS.  465 

Assuming  the  fabrication  to  be  done  in  the  field,  the  mode 
of  procedure  will  be  as  follows :  Order  the  bars  or  rods  to  be 
shipped  in  bundles  of  corresponding  sizes  and  lengths  of 
pieces  with  each  bundle  tagged  with  its  proper  shop  number 
or  mark.  The  bundles  should  weigh  about  200  Ibs. ;  this  is  a 
load  easily  handled  by  two  men  and  so  long  as  possible  all 
handling  should  be  done  in  the  original  package,  for  when 
once  broken  it  is  very  hard  to  get  men  to  carry  a  full  load. 
As  received,  the  bars  of  each  size  and  length  should  be  stored 
by  themselves.  For  ordinary  bars  not  having  long  prongs  a 
rack  of  the  general  form  shown  by  Fig.  207  serves  the  pur- 
pose excellently.  When  a  great  deal  of  metal  must  be  kept 
stored  for  some  time  it  is  wise  to  roof  over  the  racks,  not  only 
to  protect  the  metal  from  rain  and  snow,  but  to  enable  the  men 
to  work  dry  shod  in  stormy  weather.  Usually  it  will  pay  to 
have  one  man  whose  s'ole  duty  it  is  to  receive  and  check  all 
metal  and  to  attend  to  its  systematic  arrangement  on  the 
racks ;  this  same  man  will  also  direct  the  removal  of  the  metal 
to  the  shop  where  it  is  bent  and  otherwise  worked  up,  and 
can,  if  he  is  competent,  earn  his  pay  many  times  over  in  time 
saved  all  along  the  line  in  handling  and  working  up  the  rein- 
forcement. The  authors  have  seen  enough  time  wasted  in 
hauling  over  and  rehandling  metal  in  piles  to  get  at  what  was 
wanted  to  pay  for  shed,  racks  and  the  wages  of  a  storekeeper 
several  times  during  a  moderate  sized  job.  In  large- work  pro- 
vide the  storekeeper  with  a  schedule  showing  the  order  in 
which  the  metal  is  wanted  for  the  work  so  that  he  can  arrange 
it  in  that  Order  and  can  check  up  his  receipts  from  the  mills 
and  report  missing  items  in  time  for  the  deficit  to  be  made  up 
before  some  part  of  the  work  has, to  be  stopped  because  of 
material  missing.  System  in  receiving  and  storing  the  metal 
is  absolutely  essential  to  rapid  and  accurate  work  at  the  bend- 
ing and  erecting  tables. 

The  work  done  'on  the  metal  consists  chiefly  of  bending. 
The  metal  can  usually  be  bent  cold,  but  for  sizes  i^-in.  and 
upward  some  makes  of  bars  require  heating;  this  can  be 
done  by  laying  the  bars  side  by  side  on  the  ground  and  arrang- 
ing sticks  and  shavings  on  top  of  them  in  a  strip  18  ins.  to  2  ft. 
wide  across  the  portion  where  the  bend  is  to  be.  Only  mod- 
erate heating  is  usually  required.  Ordinary  bending  is  a  sim- 


466 


CONCRETE    CONSTRUCTION. 


pie  process  and  can  be  done  with  very  simple  apparatus. 
Figures  208,  209  and  210  show  frequently  used  devices,  any 
of  which  can  be  made  by  an  ordinary  carpenter.  For  heavy 
bars,  \y2  and  2  ins.,  the  device  shown  by  Fig.  210,  with  its 
heavy,  swinging  beam,  is  particularly  efficient.  An  example 
of  more  elaborate  methods  is  had  in  the  following  description 
of  the  processes  employed  in  fabricating  girder  frames  and 
hooped  column  reinforcement  for  a  large  factory  building. 


Stvp- 


-i-"*^  ?     ~                                                             ?   s       r 

r  •.•.•;•  T  •  r  T 

3    V< 

ps^  ±gfe 

-/y^/p  / 

A>w 

li  ,- 

)^  

h  ' 

Fig.  208.— Table  for  Bending 
Reinforcing  Bars. 


Fig.   209. — Table  for  Bending 
Reinforcing  Bars. 


The  building  was  500  x  75  ft.,  with  six  stories  and  a  basement, 
built  for  the  Bush  Terminal  Co.,  Brooklyn,  N.  Y.,  in  1905. 
Three  longitudinal  rows  of  round  columns  and  two  rows  of 
rectangular  wall  columns  carry  heavy  longitudinal  girders 
supporting  floor  slabs  with  corrugated  undersides  as  shown 
by  Fig.  211,  which  also  shows  the  floor  slab  reinforcement. 


n 


•Lzr 


Fig.   210.— Table  for  Bending  Reinforcing  Bars. 


About  12,000  cu.  yds.  of  concrete  and  1,000  tons  of  reinforcing 
steel  were  required ;  hence  167  Ibs.  of  steel  were  required  for 
each  cubic  yard  of  concrete.  The  floors,  however,  were  de- 
signed to  carry  a  load  of -800  Ibs.  per  sq.  ft.  The  particular 
feature  of  interest  in  this  building  was  the  fabrication  of  all 
the  column  and  girder  reinforcement  into  unit  frames  and 
cylinders  in  temporary  workshops  on  the  site. 


REINFORCED    CONCRETE    BUILDINGS. 


467 


The  circular  interior  columns,  varying  from  30  ins.  to  12  ins., 
in  diameter  were  molded  in  permanent  shells  of  cinder  con- 
crete. The  shells  were  made  in 
sections  about  30  ins.  long, 
with  walls  i  J/2  ins.  thick,  which 
were  set  one  on  another  with 
mortar  joints  to  form  the  col- 
umn mold.  In  fabricating  the 
shells  the  first  step  was  to  wind 
a  helix  of  steel  wire  on  a  col- 
lapsible mandrel  about  4  ft. 
long;  the  mandrel  was  set 
with  the  axis  horizontal  and 
was  revolved  by  hand,  the  wire 
being  fed  on  also  by  hand  and 
under  a  slight  tension.  After 
the  wire  helix  was  completed  it 
was  wrapped  with  a  sheet  of 
expanded  metal,  the  longitudi- 
nal edges  of  which  lapped 
a  few  inches  and  were  tied  by 
wire  ties.  The  expanded  metal 
covering  was  also  wire  tied  to 
the  helix.  Each  of  these  cylin- 
ders of  expanded  metal  and 
wire  was  30  ins.  long  and 
formed  the  inner  mold  for  mak- 
ing the  shell.  The  outer  mold 
consisted  of  a  sheet  metal  cyl- 
inder in  two  parts  assembled 
and  supported  by  wooden 
yokes  and  framework.  The 
two  molds  were  as'sembled  on 
a  plank  platform,  one  inside 
the  other,  and  about  a  common 
center.  The  annular  space  was 
Fig.  211.— Column  and  Floor  Slab  then  filled  with  a  1-5  cinder 
Construction  for  Factory  Building.  concrete  mixed  moderately  dry 

so  that  while  it  would  exude  slightly  through  the  expanded 
metal  mesh  it  would  not  waste  to  any  extent.    After  from  18 


468 


CONCRETE    CONSTRUCTION. 


to  24  hours  the  outer  mold  was  removed  for  reuse  and  the 
shell  was  left  standing  on  the  molding  platform  until  safe  to 
handle.  The  larger  shells,  30  x  30  x  il/2  ins.,  weighed  about  150 
Ibs.  each. 

Some  2,000,000  Ibs.  of  plain  round  steel  rods  from  *4  in.  to 
il/2  ins.  in  diameter  were  required  for  reinforcing  the  con- 
crete. For  the  main  girders  these  rods  were  cut,  bent  and 
assembled  into  frames  or  trusses  which  were  placed  as  units. 
The  main  rods  were  ordered  cut  to  length,  but  the  stirrup  rods 
were  ordered  in  lengths  of  20  ft.  and  cut  to  lengths  as  re- 
quired. The  rods  were  brought  to  the  work  in  carload  lots 


<-v                                    Working  Table 

(o  )  ( 

Fig.  212.— Device  for  Bending  Reinforcing  Rods. 

and  were  stored  according  to  lengths  and  sizes  in  racks  under 
sheds.  Another  shed  was  provided  for  the  steelworkers,  who 
cut  and  bent  the  rods  and  assembled  the  girder  frames  ready 
for  the  workmen  on  the  building.  There  were  about  50  dif- 
ferent patterns  of  frames  required.  They  were  made  entirely 
by  hand.  For  bending  large  size  rods,  heavy  compound  levers 
were  used ;  the  lighter  rods  were  bent  by  the  device  shown 
in  Fig.  212.  The  assembling  of  the  trusses  was  accomplished 
as  shown  by  Fig.  213,  using  the  steel  framework  of  the  erec- 
tion shed  as  a  staging.  Across  the  horizontals  of  the  frame- 
work were  placed  two  false  temporary  top  chord  bars  marked 


REINFORCED    CONCRETE    BUILDINGS. 


469 


to  the  stirrup  spacing  of  the  truss  being  assembled.  On  these 
bars,  at  the  spaces  marked,  were  suspended  stirrups  with  their 
lower  ends  hooked.  The  lower  chord  bars  were  then  suspend- 
ed in  the  stirrup  hooks  and  the  whole  assemblage  of  bars  and 
stirrups  was  then  qlamped  rigid  by. the  lever  bars  and  inter- 
mediate clamps.  The  loop  ends  of  the  stirrups  were  then 
bent  by  special  wrenches  to  the  position  shown  at  2,  then 
closed  by  hammering  to  the  position  shown  at  j,  and  finally 


-Framework  of  Shed 

Fnlse.tempornry  t.c.  Bnra 


0 


Locking;  Hook 


\ 


ATTACH  MEf 
TO  LOWER 


.  Lever  Bar 


1  r   Bnrs' 

STIRRUPS 

BARS 


Stirrup 


Tnw*8lld! 


HORD 


Set  Sere 


.•rew^jym 


LiwerOliord 
Bars 


INTERMEDIATE  CLAMP 
FOR  LOWER  CHORD  BARS 

Fig.     213.— Sketches    Showing    Methods    of    Fabricating    Girder    Reinforcing 

Frames. 

they  were  wire  tied.  The  process  was  a  simple  one,  and  by 
adopting  a  regular  routine  the  men  became  so  expert  that  two 
of  them  could  complete  many  trusses  in  a  working  day.  The 
contract  price  for  shaping  the  steel  and  assembling  it  into 
frames  was  i  ct.  per  Ib. ;  the  cost  of  the  work  to  the  con- 
tractor has  been  stated  by  Mr.  E.  P.  Goodrich,  Engineer, 
Bush  Terminal  Co.,  to  have  been  about  ^4  ct-  Per  It).  The  cost 
of  placing  the  steel  in  the  building  was  J4  ct-  Per  lb. 


470  CONCRETE    CONSTRUCTION. 

PLACING. — With  unit  frame  reinforcement  the  number, 
size  and  location  of  the  bars  have  been  made  certain  in  the 
shops  where  the  frames  are  fabricated  so  that  the  erector 
has  nothing  to  da  but  to  line  and  level  up  the  frames  in  the 
forms,  place  such  temporary  braces  as  are  needed  to  hold  them 
true,  and  make  the  end  connections  with  abutting  frames. 
Such  frames  are  usually  provided  with  "chairs"  to  hold  the 
bottom  bars  up  from  the  form  so  that  little  bracing  or  none 
is  requir-ed.  With  separate  bar  reinforcement  the  erector  may 
either  place  ther  reinforcement  complete  in  the  form  by  wire- 
tying  the  bars  to  each  other,  to  temporary  braces  or  templates 
and  to  the  forms,  or  he  may  insert  the  various  pieces  of 
reinforcement  in  the  concrete  as  the  pouring  advances,  depend- 
ing on  the  surrounding  concrete  to  retain  them  where  in- 
serted. Generally  a  combination  of  both  methods  is  employed. 

The  processes  in  detail  of  placing  reinforcement  are  particu- 
larized in  several  places  in  other  sections ;  they  will  differ  for 
nearly  every  job.  Here,  therefore,  general  rules  only  will  be 
given. 

(1)  See  that  the  correct  number  and  size  of  reinforcing 
bars,  splices  and  stirrups  are  used  and  that  they  are  spaced 
and  placed  strictly  according  to  the  working  plans. 

(2)  Bars  must  be  properly  braced,  supported  and  other- 
wise held  in  position  so  that  the  pouring  of  the  concrete  will 
not  displace  them. 

(3)  Splices    are    the    critical    parts    of    column    reinforce- 
ment.    See  that  the  bars  butt  squarely  at  the  ends  and  are 
held  by  pipe  sleeves  or  wired  splice  bars ;    see  that  the  longi- 
tudinal rods  are  straight  and  vertical ;   see  that  the  horizontal 
ties  or  hooping  are  tight  and  accurately  spaced.   When  the  re- 
inforcement is  built  up  inside  the  form  one  side  is  left  open  for 
the  work;   ordinarily  the  column  reinforcement  will  be  fabri- 
cated into  unit  frames,  then  an  opening  in  the  form  at  the 
bottom  to  permit  splicing  will  suffice. 

(4)  Take  extreme  care  that  beam  and  girder  reinforcement 
is  placed  so  that  the  bottom  bars  lie  well  above  the  bottom 
board  of  the  mold ;  use  metal  or  concrete  block  chairs  for  this 
purpose. 


REINFORCED    CONCRETE    BUILDINGS.  471 

(5)  See  that  the  end  connections  and  bearings  of  beam  and 
girder  frames  are  connected  up  and  have  the  bearings  called 
for  by  the  plans. 

(6)  See  that  line  and  level  of  all  bars  and  of  the  reinforce- 
ment as  a  whole  are  accurate ;    make  particularly  certain  that 
expanded  metal  or  other  mesh-work  reinforcement  lies  smooth 
and  straight. 

(7)  Give  all  reinforcement  a  final  inspection  just  previous 
to  pouring  the  concrete;    this  is  particularly  essential  where 
the   reinforcement   is    placed    some   time   in   advance   of  the 
concreting. 

MIXING,     TRANSPORTING     AND     PLACING     CON- 
CRETE. 

A  reinforced  concrete  building  requires  from  0.2  to  0.5  cu. 
yd.  of  concrete  per  100  ft.  of  cubical  volume  of  the  building, 
assuming  walls,  floors  and  roof  to  be  all  of  concrete.  The 
amount  of  concrete  to  be  mixed,  transported  and  placed  is, 
therefore,  large  enough,  even  for  a  building  of  moderate  di- 
mensions, to  warrant  close  study  of  and  careful  planning  for 
this  portion  of  the  work.  A  few  general  principles  can  be 
set  down,  but  as  a  rule  there  is  one  best  way  for  each  building 
and  that  way  must  be  determined  by  individual  conditions. 

MIXING. — Concrete  for  building  work  has  to  be  of  superior 
quality  so  that  no  chances  may  be  taken  either  in  the  process 
of  mixing  or  with  the  type  of  mixer  employed.  Machine  mix- 
ing and  batch  mixers  should  always  be  employed.  Machine 
mixing  gives  generally  a  more  homogeneous  and  uniform  con- 
crete than  does  hand  mixing  and  is  cheaper.  Batch  mixers 
are  generally  superior  and  more  reliable  than  continuous 
mixers  where  a  uniformly  well  mixed  concrete  is  required. 
The  capacity  of  the  mixing  plant  is  determined  by  the  amount 
of  concrete  to  be  placed  and  the  time  available  for  placing  it. 
Its  division  and  arrangement  is  determined  by  the  area  of  the 
work  and  the  type  and  arrangement  of  the  plant  for  transport- 
ing the  materials  and  the  mixed  concrete.  The  following  gen- 
eral principles  may  be  laid  down  :  Make  the  most  use  possible 
of  gravity ;  it  is  frequently  economy  to  carry  all  materials  to 
the  top  of  bins  from  which  point  they  can  move  by  gravity 
down  through  the  mixer  to  the  hoist  buckets,  and  where 


472  CONCRETE    CONSTRUCTION. 

natural  elevations  or  basement  floors  below  street  level  permit 
gravity  handling  they  should  be  taken  advantage  of.  The 
mixing  should  be  done  as  near  the  place  of  concreting  as 
practicable ;  in  building  work  this  is  the  point  on  the  ground 
which  is  directly  under  the  forms  being  filled.  It  is,  of  course, 
impracticable  to  secure  so  direct  a  route  as  this  from  mixer 
to  forms,  but  it  can  be  more  or  less  closely  approached ;  using 
two  mixers,  for  example,  one  at  the  front  and  one  at  the  rear 
of  a  building  cuts  down  the  haul  from  hoist  to  forms  one-half. 
Other  ways  will  suggest  themselves  upon  a  little  thought.  In 
the  matter  of  the  mixing  itself,  it  must  never  be  forgotten  that 
a  batch  of  concrete  without  cement  which  goes  into  a  girder 
or  column  will  result  in  the  failure  of  that  member  and  pos- 
sibly the  failure  of  the  building.  In  massive  concrete  work  a 
batch  without  cement  will  not  endanger  the  stability  of  the 
structure,  but  in  column  and  floor  work  in  buildings  it  is  cer- 
tain disaster.  Formanship  at  the  mixer  is,  therefore,  highly 
important  and  a  cement  man  who  realizes  the  responsibility  of 
his  task  is  equally  important. 

TRANSPORTING.— Transporting  the  mixed  concrete  is 
divided  into  three  operations — delivering  concrete  from  mixer 
to  hoist,  hoisting,  and  delivering  hoisted  concrete  to  the  forms. 
The  delivery  from  mixer  to  hoist  may  be  by  direct  discharge 
into  hoist  bucket,  by  carts  or  wheelbarrows,  or  by  cars  carry- 
ing concrete  or  concrete  buckets.  Hoisting  may  be  done  by 
platform  hoists  or  elevators,  by  bucket  hoists,  or  by  derricks. 
Handling  from  hoist  to  form  may  be  direct  in  buckets,  by  carts 
or  wheelbarrows,  or  by  cars.  These  several  methods  can  be 
worked  in  various  combinations,  and  the  following  examples 
of  plants  show  such  combinations  as  are  most  typical  of  cur- 
rent practice. 

In  any  system  of  transportation  it  is  getting  the  concrete  to 
the  hoist  and  from  hoist  to  form  that  eats  up  the  money. 
Hoisting  makes  but  a  small  part  of  the  total  transportation 
cost,  and,  moreover,  the  difference  in  cost  of  operation  for 
different  hoists  is  very  small.  Mr.  E.  P.  Goodrich  states  that 
on  three  buildings  the  actual  costs  for  the  hoists  installed  and 
removed  after  the  completion  of  the  work  were  as  follows : 


REINFORCED    CONCRETE    BUILDINGS.  473 

Platform   hoist    $33O 

Bucket  hoist 465 

Derrick    225 

In  figuring  on  the  form  of  hoist  to  be  adopted,  the  capability 
of  the  hoist  for  general  service  has  to  be  kept  in  mind.  Plat- 
form hoists  and  derricks  can  be  used  for  hoisting  form  lumber 
and  reinforcing  steel  as  well  as  for  hoisting  concrete,  while 
bucket  hoists  cannot  be  so  used  except  where  they  may  be 
fitted  with  special  carriages  for  lumber  or  steel.  On  the  other 
hand,  the  bucket  hoist  is  usually  the  quickest  method  of  hoist- 
ing concrete,  and  it  can  readily  be  extended  upward  as  the 
work  progresses.  The  last  is  true  also  of  platform  hoists.  The 
use  of  derricks  necessitates  frequent  shifting  for  high  work  or 
else  the  building  of  expensive  staging  to  raise  the  derrick  into 
a  position  to  command  the  final  height  of  the  building.  The 
probable  costs  of  moving  and  extending  must  be  allowed  for 
in  choosing  the  hoist  to  be  used. 

Direct  discharge  of  the  mixer  into  the  hoisting  bucket  is,  of 
course,  the  ideal  manner  of  transporting  the  concrete  from 
mixer  to  hoist,  and  this  can  generally  be  obtained  by  planning, 
particularly  where  bucket  hoists  or  derricks  are  employed. 
For  platform  hoists  direct  discharge  is  impossible ;  it  can  be 
somewhat  closely  approached,  however,  r  where  conditions 
permit  car  tracks  to  be  laid  on  the  floors  being  built,  so  that 
a  car  holding  a  batch  of  concrete  can  be  run  onto  the  platform, 
hoisted  and  then  run  to  shoveling  boards  near  the  forms  that 
are  being  filled.  The  successful  use  of  such  an  arrangement 
of  car  tracks  is  described  in  Chapter  XX,  but  it  was  for 
handling  concrete  blocks.  A  direct  discharge  from  hoisting 
bucket  to  forms  is  frequently  possible  where  derricks  are  used 
for  hoisting,  but  with  bucket  and  platform  hoists,  wheeling 
or  carting  is  necessary. 

Where  wheeling  or  carting  has  to  be  done  either  at  the  bot- 
tom or  at  the  top  of  the  hoist,  or  at  both  points,  a  great  factor 
in  the  economy  of  work  is  the  arranging  of  the  operations  in 
cycles.  For  example,  in  wheeling  concrete  to  forms  from  a 
hopper  fed  by  a  bucket  hoist,  arrange  the  runways  so  that 
each  man  makes  a  circuit,  passing  by  the  form  at  one  end 
and  by  the  hopper  at  the  other  end,  and  goes  and  comes  by  a 
different  route.  The  speed  gained  by  avoiding  confusion  and 


474 


CONCRETE    CONSTRUCTION. 


delay  saves  many  times  the  additional  cost  of  runways  which 
is  small.  In  fact  it  is  economy  to  employ  a  few  extra  men 
to  arrange  runways  and  keep  them  clean,  because  of  the  addi- 
tional speed  thus  gained.  Good  organization  effects  more 
economy  than  special  methods  of  hoisting  as  far  as  the  labor 
of  handling  the  concrete  is  concerned. 

Bucket  Hoists. — A  bucket  hoist  construction  which  has  been 
extensively  used  in  build- 
ing work  on  the  Pacific 
coast  is  shown  by  the  draw- 
ings of  Figs.  214  to  216. 
Twt)  T-bar  guides  made  in 
sections  connected  by  fish- 
plates furnish  a  track  for  an 
automatic  dumping  bucket 
hoisted  and  lowered  by  steel 
cable  from  engine  on  the 
ground  to  head  sheaves  as 
shown.  The  sectional  con- 
struction of  the  T-bar  guides 
permits  the  hoist  to  be  any 
height  "desired,  it  being- 
lengthened  and  shortened  by 
adding  and  taking  out  sec- 
tions. The  bucket  is  dumped 
automatically  at  any  point 
desired  by  means  of  a  trip- 
ping device  attached  to  a 
chute  which  receives  the 
contents  of  the  bucket  and 
delivers  them  to  carts, 
wheelbarrows,  or  other  re- 
ceptacle. The  hoist  is  set 
outside  of  the  building  with  the 
sible,  to  discharge  directly  into 
the  guide  frame  in  a  pit  or  on 
edge  of  bucket  can  be  secured. 


214.— Bucket  Hoist  for  Building 
Work   (Wallace-Lindesmith). 

mixer    arranged,    if    pos- 
the    bucket.     By    setting 
blocking    any    height    of 
The    buckets    are  ordi- 


narily 13^  or  20  cu.  ft.  capacity.  It  is  recommended, 
when  greater  hoisting  capacity  is  necesrary,  to  use  two  hoists 
set  side  by  side  and  operated  by  one  cable  in  the  same  manner 


REINFORCED    CONCRETE    BUILDINGS. 


475 


as  double  wheelbarrow  cages ;  as  the  weight  of  one  bucket 
counterbalances  the  weight  of  the  other,  the  power  required  for 
hoisting  is  reduced.  To  adapt  this  hoist  to  handling  form 
lumber  the  bucket  is  replaced  by  the  lumber  carriage  shown 
by  Fig.  216;  this  carriage  discharges  over  the  head  of  the 
mixer  and  the  spring  buffer  shown  by  Fig.  214  is  to  take  the 
shock  of  the  rising  carriage.  This  buffer  is  omitted  when 
concrete  only  is  to  be  hoisted.  In  one  case  this  device  has 
hoisted  520  batches  of  12  cu.  ft.  each  to  the  fourth  floor  in 
8  hours,  or  nearly  19  cu.  yds.  per  hour.  In  another  case  65 
trips  per  hour  were  averaged  to  the  fifth  floor  with  a  12-cu.  ft. 


Fig,    215.— Wallace-Lindesmith  Hoist 
Bucket  in  Discharging  Position. 


Fig.  216. — Lumber  Carriage  for 
Wallace-Lindesmith  Hoist. 


load  each  trip ;  this  is  nearly  30  cu.  yds.  per  hour.  With  the 
lumber  carriage  8  men  have  unloaded  14,000  ft.  B.  M.  of  2  x  10- 
in.  stuff  from  car  to  the  second  floor  and  distributed  it  in  43 
minutes.  A  ^-cu.  yd.  combination  outfit  for  concrete  and 
lumber,  with  40  ft.  of  guide  track,  weighs  1,750  Ibs.,  without 
the  lumber  carriage  the  outfit  weighs  1,600  Ibs.  This  hoist 
is  made  by  the  Wallace-Lindesmith  Co.,  Los  Angeles,  Cal. 

A  popular  construction  for  automatic  bucket  hoists  is  that 
shown  by  Figs.  217  and  218  by  Mr.  E.  L.  Ransome.  The 
bucket  is  held  upright  by  guides  at  its  front  and  rear  edges ;  to 


476 


CONCRETE    CONSTRUCTION. 


dump  it  a  section  of  the  front  guide  is  removed  at  the  desired 
dumping  point  which  allows  the  bucket  to  overturn  as  shown. 
A  friction  crab  hoist  operated  from  the  mixer  engine  runs  the 


Fig.  217.— Mixer  Plant  with  Gravity  Feed  from   Material   Bins  to  Hoisting 

Bucket. 

bucket.  The  mixer  is  located  as  shown.  Figure  218  shows 
the  foot  of  the  hoist  set  in  a  pit  v'i.th  the  mixer  at  surface 
level,  but  the  hoist  can  be  set  on  the  surface  and  the  mixer 


REINFORCED    CONCRETE    BUILDINGS. 


477 


mounted  on  a  platform.  In  the  latter  case  a  charging  bucket, 
traveling  from  stock  pile  up  an  inclined  track  to  the  mixer  plat- 
form, is  generally  used.  A  hoist  like  that  illustrated,  equipped 
with  a  ^-cu.  yd.  Ransome  mixer,  will  cost  about  $1,500  and 
will  deliver  15  cu.  yds.  of  concrete  per  hour.  Mr.  F.  W.  Dag- 
gett  gives  the  following  figures  of  the  cost  of  operation: 

Mixing  Gang :  Total  I  hr. 

i  mixer  foreman,  also  engineer,  25c $  .25 

i  man  charging  mixer,  2oc 20 

1  man  running  hoist,  2oc 20 

2  men  wheeling  sand,  17/^c 35 

4  men  wheeling  and  shoveling  stone,  i7>^c 70 

1  man  helping  up  runway,  17^20 

2  men  carrying  cement,   I7^c 35 

Gang  Placing  Cement : 

I  foreman,  25c 25 

9  men   wheeling  concrete,    I7^c 

3  men  tamping  concrete,  i7^>c 52^2 

i  man  filling  carts,  17^0 171^ 

Total  labor  cost  per  hour $4-75 

Fuel,  etc 50 

$5-25 

This  gives  a  cost  of  35  cts.  per  cu.  yd.  for  mixing  and  placing 
concrete. 

In  this  particular  case  the  mixer  was  charged  by  wheel- 
barrows. Frequently  the  stone  and  sand  bins  can  be  arranged 
to  chute  the  materials  directly  into  the  charging  hopper  as 
shown  by  Fig.  217.  In  place  of  barrows  two-wheeled  carts  of 
the  type  shown  by  Fig.  12  can  be  used.  Mention  has  already 
been  made  of  operating  the  charging  bucket  on  an  incline  from 
stock  pile  to  mixer.  Such  arrangements  are  described  in 
Chapter  IV. 

In  constructing  a  q-story  store  at  St.  Paul,  Minn.,  the  con- 
crete was  hoisted  by  continuous  bucket  elevators.  A  layout 
of  the  construction  plant  is  shown  by  Fig.  219.  In  the  alley 
near  the  center  of  the  north  side  of  the  building  the  surface 
was  about  6  ft.  above  the  third  story  level.  A  hopper 


478 


CONCRETE    CONSTRUCTION. 


was  constructed  at  grade  and  provided  with  two  chutes  run- 
ning to  the  basement.     These  chutes  discharged  on  opposite 
sides  of  a  vertical   partition   separating  the   sand   and   stone 
bins,  and  by  closing  either  chute  at  its  top  by  a  suitably  ar- 
ranged deflector  plate  either  sand  or  stone  could  be  dumped 
into  the  same  hopper  and 
chuted  to  its  proper  bin. 
Cement   was    brought   to 
the  work  in  cars  over  the 
tracks     shown     and    was 
wheeled     from     the     cars 
over   runways   leading  to 
the     charging     platforms 
near   each   mixer.      Other 
runways  connecting  with 
these   platforms   provided 
for  wheeling  the  sand  and 
stone  to  the  mixers.    The 
runways   were    placed    at 
the  proper  height  to  per- 
mit   the    barrows    to    be 
emptied  directly   into  the 
charging     hoppers.     Two 
Smith   mixers  were  used, 
located     as     shown,     and 
each    discharged   through 
a   chute   into   one   of   the 
bucket      elevator      boots. 
There  were  two  elevators 
which  were  "raised"  two 
Stories  at  a   move  as  the 
work     progressed.     Each 
efevator    discharged    into 
a     hopper     holding     \y2 
batches,    and    from    these 
hoppers     the     concrete    was     fed     into     wheelbarrows     and 
wheeled   to   the   forms.    The   bucket   elevators   were    carried 
no  higher  than  the  eighth  floor.     When  this  floor  had  been 
completed  the  hoppers  were  moved  down  to  the   fifth  floor 
and  the  wheelbarrows  were  taken  to  platform  elevators  and 


Fig.   218— Bucket  Hoist  for  Building 
Work   (Ransome). 


REINFORCED    CONCRETE    BUILDINGS 


479 


carried  to  the  remaining  floors  and  roof.  Special  4-cu.  ft. 
wheelbarrows  were  used  for  handling  the  concrete.  A  maxi- 
mum of  155  cu.  yds.  of  concrete  was  mixed,  transported  and 
placed  in  a  lo-hour  day  with  a  gang  of  28  men. 

Platform  Hoists. — The  common  builders'  hoist  or  elevator, 
operating  single  or  double  platforms  or  cages,  needs  no  spe- 
cial description.  The  wheelbarrow,  cart  or  car  containing  the 
concrete  is  run  onto  the  platform,  hoisted  and  then  run  to  the 
forms.  The  chief  advantage  of  this  device  in  concrete  work  is 
that  it  will  handle  all  classes  of  material  without  any  change 
of  carriage  or  arrangement,  it  can  thus  be  used  for  handling 
form  lumber  and  reinforcing  steel  as  well  as  for  handling 
concrete. 


Hopper 


.Section    A-B 

Sedtionol  Plan. 

Fig.  219.— Plan  of  Concrete  Mixing  and  Handling  Plant  for  9 -Story  Building. 

Derricks. — The  use  of  derricks  for  hoisting  in  concrete 
building  work  is  limited  by  the  necessity  of  supporting  them 
independently  of  the  structure  being  built ;  the  formwork  or 
the  completed  concrete  work  cannot  be  utilized  to  carry  der- 
ricks during  construction.  For  low  structures  the  derrick  can 
be  set  on  the  ground,  but  for  high  buildings  a  supporting 
tower  or  staging  is  necessary.  The  arrangement  of  such 
falsework  can  be  illustrated  best  by  specific  examples. 

In  constructing  a  /-story  factory  at  Cincinnati,  O.,  concrete 
was  mixed  on  the  ground  and  hoisted  by  a  derrick  with  an 
8o-ft.  boom  mounted  on  a  tower  55  ft.  high.  The  derrick 
was  located  to  one  side  of  the  building.  For  the  lower  floors 
the  boom  swing  covered  so  large  an  area  that  the  bucket  was 
dumped  at  various  places,  but  for  the  upper  floors  it  was  found 


480  CONCRETE    CONSTRUCTION. 

more  economical  to  dump  buckets  into  a  hopper  from  which 
wheelbarrows  were  filled.  By  this  plan  less  time  was  con- 
sumed in  placing  the  bucket  and  no  tag  rope  man  was  re- 
quired, as  the  engineman  could  swing  the  boom  to  a  certain 
point  on  the  wall  which  would  bring  the  bucket  directly  over 
the  hopper.  A  Smith  mixer  discharged  directly  into  derrick 
buckets,  which  rested  on  a  track  long  enough  to  hold  two 
buckets.  The  buckets  were  filled  and  emptied  alternately  by 
shuttling  the  truck  and  attaching  first  one  and  then  the  other 
to  the  derrick. 

In  constructing  an  n-story  and  basement  office  building  in 
New  York  City  a  four-legged  tower  starting  from  the  bottom 
of  the  excavation  was  erected  at  about  the  center  of  the  lot. 
It  was  built  of  timber  and  extended  upward  as  the  progress  of 
the  work  demanded  until  it  overtopped  the  roof  n  stories 
above  the  street.  The  tower  was  square  in  plan  and  was 
divided  into  stories  corresponding  approximately  to  the  several 
stories  of  the  building.  A  floor  was  constructed  in  the  tower 
at  each  story  to  be  used  in  storing  materials.  For  hoisting 
a  75-ft.  boom  was  swung  from  each  leg  of  the  tower,  each 
boom  being  operated  by  a  separate  engine  and  having  a  nom- 
inal capacity  of  5  tons.  The  four  booms  covered  the  whole 
building  area  and  were  kept  about  two  stories  above  the  work 
by  being  shifted  upward  as  the  work  progressed.  This  ar- 
rangement of  derricks  was  used  to  handle  the  steel,  lumber 
and  concrete,  the  building  being  built  up  around  the  tower, 
which  was  so  located  that  its  only  interference  with  the  build- 
ing structure  was  in  the  shape  of  square  holes  left  in  the 
floor  slabs  to  accommodate  the  tower  legs. 

In  constructing  an  8-story  warehouse  covering  some  three 
acres  of  ground  in  Chicago,  111.,  the  derrick  plant  shown  by 
Figs.  220  to  222  was  installed.  Some  7,500  tons  of /reinforc- 
ing steel,  125,000  cu.  yds.  of  concrete  and  4,000,000  ft.  of  form 
lumber  had  to  be  handled.  Incidentally  it  is  worth  noting  that 
there  were  about  120  Ibs.  of  reinforcing  steel  and  32  ft.  B.  M. 
of  form  lumber  used  per  cubic  yard  of  concrete. 

The  controlling  conditions  governing  the  arrangement  and 
character  of  the  construction  plant  were  as  follows :  The 
building,  to  be  built  entirely  of  reinforced  concrete,  was  135  ft. 
high.  Its  west  front  abutted  on  the  river  and  its  south  front 


REINFORCED    CONCRETE    BUILDINGS. 


481 


on  the  street ;  at  the  north  end  there  was  some  ground  avail- 
able for  plant  and  along  the  east  front  there  was  a  strip  about 
20  ft.  wide  between  the  building  wall  and  the  main  line  tracks 
of  a  railway.  At  best,  therefore,  the  area  outside  of  the  build- 
ing and  available  for  plant  and  storage  was  limited,  while  in- 
side the  building  area  the  contractor  was  confronted  by  the 
insistence  of  the  architect  that  an  unbroken  monolithic  con- 
struction be  obtained  as  nearly  as  possible,  by  reducing  the 
floor  openings  for  construction  work  to  a  minimum.  The 
sketch  plan,  Fig.  220,  shows  the  plant  designed  to  meet  the 
conditions. 

To  get  the  large  amount  of  construction  material  onto  the 
work  a  side  track  was  built  along  the  2O-ft.  area  on  the  east 
side  of  the  building  and  another  was  turned  into  the  area  at 


R  I   V  E  * 


Eng.  Contr. 


Fig.  220.— Plan  of  Concrete  Mixing  and  ^Handling  Plant  for  Large  Warehouse 

the  north  end  of  the  building.  These  side  tracks  handled  all 
construction  materials  coming  onto  the  work.  Over  the  first, 
there  were  built  two  sets  of  storage  bins  for  sand  and  gravel 
and  all  concrete  materials  brought  in  in  carload  lots  are  un- 
loaded at  these  two  points,  as  will  be  described  further  on. 
Lumber  for  forms  and  steel  for  reinforcement  shipped  in  sim- 
ilar manner  were  taken  by  the  second  siding  to  the  lumber 
yard  and  steel  mill  at  the  north  end  of  the  building. 

The  raw  materials  after  being  worked  up  in  the  mixer  plants 
and  the  saw  and  steel  mills  were  distributed  over  the  work 
by  an  industrial  railway.  The  track  system  of  this  railway 
is  shown  by  the  dotted  lines;  it  was  located  on  the  basement 


482 


CONCRETE    CONSTRUCTION. 


Fig.  221.— Derrick  for  Handling  Concrete  for  Large  Warehouse  Building. 


REINFORCED    CONCRETE    BUILDINGS.  483 

floor,  with  rampes  leading  to  the  No.  i  mixer  plant  and  to  the 
saw  and  steel  mill  tracks.  The  two  main  lines  of  track  passed 
close  to  or  under  the  elevator  and  stairway  shaft  openings  in 
the  several  floors.  This  permitted  the  derrick  buckets,  low- 
ered and  hoisted  through  the  shafts,  to  be  loaded  directly  from 
the  car  tracks.  All  mixed  concrete,  forms  and  reinforcing 
frames  were  distributed  by  this  railway  to  the  several  shafts 
and  thence  hoisted  and  placed  by  the  derrick  plant. 

The  derrick  plant  consisted  of  four  derricks  arranged  as 
shown  by  the  circles  in  Fig.  220.  The  view,  Fig.  221  shows 
the  first  derrick  installed  and  illustrates  the  general  construc- 
tion quite  clearly.  Briefly  the  derrick  consisted  of  a  vertical 
steel-work  tower  10  ft.  square  and  85  ft.  high,  within  which 
operated  a  steel  mast  135  ft.  high  and  carrying  an  8o-ft.  boom 
connected  just  above  the  tower.  The  mast  was  pivoted  at  the 
bottom  and  had  rollers  turning  against  a  horizontal  ring  inside 
the  tower  at  the  top.  It  was  operated  by  a  bull  wheel  above 
the  top  of  the  tower,  the  turning  ropes  running  down  inside 
the  mast  to  the  foot  block  and  thence  horizontally  to  the 
operating  motor.  The  topping  and  hoisting  lines  also  followed 
this  route.  The  top  of  the  tower  was  guyed  by  four  ropes  to 
anchorages  in  the  basement  floor.  The  boom  commanded  a 
circle  170  ft.  in  diameter  and  could  lift  150  ft.  above  the  base 
of  the  mast.  The  derrick  was  operated  by  a  25-HP.  double 
drum  electric  hoist  with  a  derrick  swinging  spool ;  this  hoist 
was  set  on  the  basement  floor.  It  will  be  noted  that  the  guys 
are  below  the  bull  wheel  so  that  the  boom  has  a  clear  swing 
through  a  complete  circle. 

As  stated  above,  four  of  these  derricks  were  employed.  To- 
gether they  did  not  cover  the  entire  building  area,  but  by  the 
use  of  a  derrick  bucket  so  designed  that  it  could  be  used  as  a 
storage  bin  for  feeding  wheelbarrows,  it  was  found  possible 
to  keep  the  number  of  derricks  down  to  four. 

This  derrick  plant  possessed  several  advantages  of  import- 
ance. In  the  first  place  the  derricks  would  handle  all  classes 
of  material — concrete,  forms,  steel  frames — equally  well  and 
could  be  transferred  from  one  class  of  work  to  the  other  with 
practically  no  delay.  In  the  second  place,  for  a  large  area  of 
the  building,  they  handled  the  material  from  the  basement  di- 
rect to  the  place  it  was  to  occupy  in  the  work,  and  did  it  in 


484  CONCRETE    CONSTRUCTION. 

one  operation.  Finally  they  permitted  the  handling  and  erec- 
tion of  the  forms  and  reinforcement  in  large  units.  Thus  a 
column  form  would  be  assembled  complete  at  the  mill,  moved 
as  a  unit  by  car  to  the  proper  shaft  and  then  hoisted  and  set 
in  place  as  a  unit  by  the  derrick.  Girder  forms,  floor  slab 
forms,  girder  and  column  reinforcing,  etc.,  could  be  similarly 
assembled  and  handled.  The  derricks  occupied  only  the  area  of 
four  floor  panels,  the  remainder  of  the  area  of  each  floor  was 
left  unobstructed  for  the  work  to  be  done.  No  materials  or 
supplies  needed  be  stored  on  the  floors  until  they  were  in  per- 
fect condition  to  accommodate  them,  and  not  then,  even,  so 
far  as  the  prosecution  of  form  erection  and  concreting  were 
concerned. 

The  sand  and  gravel  for  concrete  were  brought  in  by  bot- 
tom or  side  dump  gondola  cars  from  pits  located  about  30 
miles  out  on  the  Chicago,  Milwaukee  &  St.  Paul  Ry.  The 
cars  were  switched  onto  the  main  side  track  and  unloaded  un- 
der the  bins  which  straddle  this  track. .  A  receiving  hopper, 
with  its  top  at  rail  level  and  long  enough  to  permit  two  cars 
to  be  unloaded  at  once,  received  the  sand  or  gravel  and  dis- 
tributed it  through  twelve  gate  openings  onto  an  i8-in.  hori- 
zontal belt  conveyor  65  ft.  long.  This  conveyor  discharged 
into  a  second  conveyor,  133  ft.  long,  which  ran  up  a  22°  in- 
cline, extending  away  from  the  bins  and  discharged  onto  a 
third  conveyor  117  ft.  long,  which  doubled  back  on  a  22°  in- 
cline reaching  to  and  over  the  top  of  the  bins.  This  third 
conveyor  had  two  fixed  trippers  and  an  end  discharge  to  dis- 
tribute its  cargo.  All  three  conveyors  were  operated  by  a  35- 
HP.  motor  located  at  the  junction  of  the  two  inclined  convey- 
ors, both  of  which  were  driven  from  the  same  shaft.  A  chain 
belt  from  the  idler  shaft  of  the  first  incline  conveyor  to  the 
driving  shaft  of  the  horizontal  conveyor  operated  that  unit  of 
the  plant.  This  belt  was  operated  as  a  cross  belt  by  reversing 
alternate  links.  No  manual  labor  was  required  to  handle  the 
sand  and  gravel  from  the  cars  to  the  storage  bins. 

The  mixer  arrangement  at  the  two  bins  differed.  At  the  No. 
I  bins  the  mixer  was  located  as  shown  in  Fig.  220,  close  to  the 
bin.  Chutes  led  directly  from  the  sand  and  gravel  bins  to  the 
charging  hopper  and  the  bags  of  cement  were  stacked  along- 
side this  hopper.  The  mixer  discharged  either  directly  into 


REINFORCED    CONCRETE    BUILDINGS. 


485 


the  bucket  of  the  first  derrick  or  into  cars  for  transportation 
on  the  railways.  At  the  No.  2  bins  a  belt  conveyor  took  the 
concrete  materials  down  into  the  basement  to  a  mixer  located 
close  enough  to  one  of  the  distribution  tracks  to  permit  it  to 
discharge  directly  into  the  cars. 

The  derrick  buckets  by  which  the  concrete  was  hoisted  and 
handled  to  the  work  were  of  special  construction.  A  bucket 
was  desired  which  would  serve  several  distinct  purposes.  It 


Fig.    222. — Special    Concrete   Bucket   for   Large   Warehouse   Building. 

must  first  be  able  to  hold  a  full  mixer  batch  of  material,  since, 
with  the  derrick  arrangement,  economy  in  hoisting  necessi- 
tated hoisting  in  large  units  and  also  because  storage  capacity 
.was  required  of  the  bucket  for  wheelbarrow  work.  •  The  four 
derricks  did  not  command  the  entire  area  of  a  floor;  there  were 
corners  and  other  irregular  areas  outside  of  the  circles  covered 
by  the  several  booms  over  which  the  concrete  must  be  distrib- 


486  CONCRETE    CONSTRUCTION. 

uted  by  barrows  or  carts.  A  bucket  large  enough  to  supply 
the  barrows,  while  a  second  bucket  was  being  lowered, 
charged  from  the  mixer  and  hoisted,  was  required.  In  the 
second  place,  a  bucket  was  required  whose  contents  could  be 
discharged  all  at  once  or  in  smaller  portion  at  will.  Finally  a 
bucket  was  desired  which  could  be  made  to  distribute  its  load 
along  a  narrow  girder  form  or  in  a  thin  sheet  for  a  floor  slab. 

To  meet  these  requirements  the  bucket  shown  in  Fig.  222 
was  designed.  It  held  42  cu.  ft.,  or  about  1.55  cu.  yds.  of 
concrete.  It  had  a  hopper  bottom  terminating  in  a  short  rec- 
tangular discharge  spout  closed  by  a  lever  operated  under  cut 
gate,  which  could  be  opened  as  much  or  as  little  as  desired.  To 
the  underside  of  the  bucket  there  was  attached  a  four-leg 
frame  in  which  the  bucket  stood  when  not  suspended.  Ordi- 
narily, that  is  within  the  circles  commanded  by  the  derricks, 
the  buckets  were  discharged  suspended  and  directly  into  the 
forms,  the  character  of  the  discharge  gate  permitting  a  thin 
sheet  to  be  spread  for  floor  slabs  or  a  narrow  girder  or  wall 
form  to  be  filled  without  spilling  or  shock.  For  wheelbarrow 
work  outside  the  reach  of  the  derricks  the  mode  of  procedure 
was  as  follows :  A  timber  platform  about  3  ft.  high  and  hav- 
ing room  for  standing  two  buckets  was  set  just  on  the  edge  of 
the  circle  commanded  by  the  derrick  boom.  Two  buckets 
were  used.  A  full  bucket  was  hoisted  and  set  on  the  platform, 
with  its  spout  overhanging.  This  bucket  served  as  a  stor- 
age bin  for  feeding  the  wheelbarrows  while  the  second  bucket 
was  being  lowered,  charged  and  hoisted  to  take  its  place  on 
the  platform,  and  serve  in  turn  as  a  storage  hopper. 

PLACING  AND  RAMMING.— A  wet  concrete  is  usually 
used  in  building  work  except  on  occasions,  for  exterior  wall 
work  and  except  for  pitch  roof  work,  where  a  wet  mixture 
would  run  down  the  slope.  Placing  and  tamping  are  there- 
fore, essentially  pouring  and  puddling  operations.  The  pour- 
ing should  be  done  directly  from  the  barrows,  carts,  or  buckets 
if  possible;  dumping  onto  shoveling  boards  and  shoveling 
makes  an  extra  operation  and  increases  the  cost  by  the  wages 
of  the  shoveling  gang.  Where  shoveling  boards  are  necessary, 
take  care  that  they  are  placed  close  to  the  forms  being  filled, 
as  it  is  wasteful  of  time  to  carry  concrete  in  shovels,  even  for 


REINFORCED    CONCRETE    BUILDINGS.  487 

a  half  dozen  paces.  Before  pouring  any  concrete,  the  inside  of 
the  forms  should  be  wet  down  thoroughly  with  a  hose  or 
sprinkler,  if  a  hose  stream  is  not  available.  The  final  inspec- 
tion of  forms  and  reinforcement  just  before  concreting  will 
have  made  certain  that  they  are  ready  for  the  concrete,  so  far 
as  line  and  level  of  forms  and  presence  and  proper  arrange- 
ment of  the  reinforcement  are  concerned,  but  the  concrete 
foreman  must  watch  that  no  displacement  occurs  in-  pouring 
and  puddling,  and  must  make  certain  particularly  that  the 
forms  are  clean. 

In  pouring  columns  it  is  essential  that  the  operation  be 
continuous  to  the  bottom  of  the  beam  or  girder.  It  is  also  ad- 
visable to  pour  columns  several  hours  ahead  of  the  girders. 
Puddling  should  be  thorough,  as  its  purpose  is  to  work  the 
concrete  closely  around  the  reinforcement  and  into  the  angles 
of  the  mold  and  to  work  out  air  bubbles.  A  tool  resembling  a 
broad  chisel  is  one  of  the  best  devices  for  puddling  or  slicing. 
In  slab  and  girder  construction,  the  pouring  should  be  con- 
tinuous from  bottom  of  girder  to  top  of  slab.  Work  should 
never  be  stopped-off  at  horizontal  planes.  As  in  columns, 
careful  puddling  is  essential  in  pouring  beams.  In  slab  work, 
the  concrete  is  best  compacted  by  tamping  or  rolling.  A 
broad  faced  rammer  should  be  used  for  tamping  wet  concrete, 
or  a  wooden  roller  covered  with  sheet  steel,  weighing  about 
250  Ibs.,  and  having  a  3O-in.  face. 

Theoretically,  concreting  should  be  a  continuous  operation, 
but  practically  it  cannot  be  made  so.  Bonding  fresh  concrete 
to  concrete  that  has  hardened,  though  it  has  been  done  with 
great  perfection  by  certain  methods  as  described  in  Chapter 
XXIV,  must  still  be  held  as  uncertain.  Ordinarily,  at  least, 
a  plane  of  weakness  exists  where  the  junction  is  made  and 
in  stopping  off  work  it  should  be  done  where  these  planes  of 
weakness  will  cause  the  least  harm.  Experts  are  by  no  means 
agreed  on  the  best  location  of  these  planes,  but  the  following  is 
recognized  good  practice.  Work  once  started,  pouring  a 
column,  should  not  be  stopped  until  the  column  is  completed 
to  the  bottom  of  the  girder.  For  beams  and  girders ;  stop  con- 
crete at  center  of  girder  with  a  vertical  face  at  right  angles  to 
the  girder,  or  directly  over  the  center  of  the  columns ;  in 
beams  connecting  with  girders,  stop  concrete  at  center  of 


CONCRETE    CONSTRUCTION. 


span,  or  directly  over  center  of  connecting  girder;  stop  al- 
ways with  a  vertical  face  and  never  with  a  sloping  face,  and 
never  with  a  girder  partly  rilled.  For  slabs ;  stop  concrete 
at  center  of  span,  or  directly  over  middle  of  supporting  girder 
or  beam ;  stop  always  with  vertical  joints.  If  for  any  cause 
work  must  be  stopped  at  other  points,  than  those  stated,  the 
fresh  concrete  and  the  hardened  concrete  must  be  bonded  by 
one  of  the  methods  described  in  Chapter  XXIV. 

CONSTRUCTING  WALL  COLUMNS  FOR  A  BRICK 
BUILDING. — The  columns,  12  in  number,' were  constructed 
to  strengthen  the  brick  walls  of  a  power  station  and  were 
built  as  shown  by  Figs.  223  and  224,  one  at  a  time.  The  sta- 
ging, 50  ft.  high  and  4x6  ft.  in  plan,  Avas  erected  against  the 
wall  which  had  been  shored,  a  portion  of  the  wall  was  cut 
out  and  forms  erected  and  the  concrete  column  substituted  for 
the  section  of  wall  which  was  removed.  The  staging  was 
then  moved  into  position  for  another  column. 


k 2'IQ'- 

Fig.  223.— Section  of  Rectangular  Wall  Column. 

Two  men,  with  sledge  and  drill,  cut  out  the  brick  work 
amounting  to  about  12  cu.  yds.  for  each  column  in  15  hours, 
at  a  cost  of  about  70  cts.  per  cu.  yd.,  including  removal  to  the 
street.  The  cost  of  moving  and  re-erecting  the  scaffolding  was 
$2.94  per  each  move.  The  character  of  the  reinforcement  is 
shown  by  Fig.  223 ;  it  was  erected  as  the  concreting  pro- 
gressed, the  main  bars  being  in  sections  15  ft.  long,  spliced 
v/ith  and  distanced  by  side  bars  and  cross  bolts  at  the  splices. 

The  concrete  was  hand  mixed  in  6-cu.  ft.  batches  at  the  foot 
of  the  column,  by  three  men  with  a  fourth  turning  over  and 
filling  the  buckets.  The  buckets,  12  ins.  in  diameter  and 
16  ins.  high,  were  hoisted  by  a  pulley  line  arranged  as  shown 
and  pulled  by  a  mule  driven  by  a  man,  at  $i  per  day  for  the 
mule  and  $1.50  for  the  man,  the  cost  of  hoisting  being  25  to  40 


REINFORCED    CONCRETE    BUILDINGS. 


489 


Front 
'Elevation 

of 
Column  Form. 


Section  through,  Front  Wall 
Showing  Forms  and  Shoring. 


Section  through   Center* 

of    Concrete  Column 

Division  Wall.* 


Fig.  224.— Staging  and  Forms  Used  in  Building  Column   Shown  by  Fig.  223. 


490  CONCRETE    CONSTRUCTION. 

cts.  per  cu.  yd.,  depending  on  the  rapidity  of  the  man  inside 
the  form.  This  man  tamped  the  concrete  which  was  emptied 
from  the  buckets  by  a  man  on  the  scaffolding.  Each  batch 
raised  the  level  in  the  form  15  ins.,  and  between  batches  a 
set  of  ties  for  the  column  rods  was  placed  by  the  man  during 
the  tamping.  It  took  from  iJ/£  tc  2  days  to  concrete  a  column 
of  12  cu.  yds.  The  concrete  was  a  1-3.8-5.7  limestone  screen- 
ings mixture,  mixed  wet  enough  to  be  easily  pushed  into  the 
forms  and  worked  around  the  reinforcement.  The  form  con- 
struction is  shown  by  Fig.  224.  The  form  for  one  column  re- 
quired 650  ft.  B.  M.  of  lumber,  and  on  an  average,  each  form 
was  used  twice.  As  a  matter  of  fact,  the  side  strips  and  out- 
side braces  were  used  three  times,  while  much  of  the  %-in. 
sheathing  was  destroyed  by  being  used  once.  The  lumber  for 
shoring  cost  $23  per  M.  ft.  B.  M.,  and  the  light  lumber  for 
forms  cost  $18  per  M.  ft.  B.  M.  All  lumber  was  yellow  pine. 
All  labor  was  negro,  at  15  cts.  per  hour;  foremen  who  worked, 
22^  cts.  per  hour.  The  cost  of  the  several  parts  of  the  work 
compiled  from  records  furnished  by  Mr.  Keith  O.  Guthrie,  en- 
gineer in  charge,  was  as  follows: 

Cost  per  Cost  per 

Concrete.  column  cu.  yd. 

Lumber  for  forms $  4.81  $0.40 

Setting  up  and  removing  forms 11.32  0.95 

Cement,    10.17  bbls.   at  $2.40 24.40  2.03 

Sand,  5.87  yds.  at  $0.90 5.28  0.44 

Stone,  8.75  yds.  at  $1.35 10.94  0.91 

Mixing  and  wheeling   !5-73  1.31 

Hoisting  by  mule  with  driver 4.80  0.40 

Handling  bucket  on  scaffold 2.93  0.25 

Tamping  inside  column 2.93  0.25 

Painting  with  grout 3.89  0.32 

Clearing  away  rubbish   1.97  0.16 

Rigging,   etc 2.64  0.21 

Tools    0.59  0.05 

Moving  scaffold    2.94  0.25 

Moving  mix  board  and  rigging  hoist.  .      1.62  0.14 


Total  c'ost  of  concrete $96.79  $8.07 


REINFORCED    CONCRETE    BUILDINGS. 


491 


Cost  per 
Reinforcement.  column. 

Iron  bars,  1,034  Ibs $20.68 

Drilling  iron   bars 1.44 

Setting  iron  bars  in  place 1.23 

Bolts  for  splicing  and  spacing 3.98 

Wire  cross  ties  at  2.y2  cts.  Ib 1.39 

Labor  forming  130  cross  ties 1.13 

Total  cost  of  iron  and  steel $29.85 

Summary    of    Cost. 

Per  column. 

Concrete  in  place  $96.79 

Steel  in   place   29-85 

Cutting  out  and  removing  brick 8.36 

Shoring  floors  and  roof,  labor 5.87 

Ditto  for  lumber  used  3  times ; .     3.44 

Total  $144.31 


r~1 

I 

a'  xl 

7* 

•*. 
S 

§ 

• 

§ 

x 
*0 

I 

^ 

i 

% 

? 

s 

A 

-a 

\ 

\ 

4- 

—  f- 

Eng 

-c 

G'O*   
'ontr: 

W 

Cost  cts.  per 

Ib.  of  bars. 

$2.00 

0.14 

0.12 

0.40 

0.14 

c.n 

$2.91 

Per  cu  yd. 
$8.07 
2.49 
0.70 
0.49 
0.29 


Fig.    225.— Girder   Plan    for   6-Story   Building. 

FLOOR  AND  COLUMN  CONSTRUCTION  FOR  SIX- 
STORY  BUILDING.— The  building  was  91  x  112  ft.;  56  col- 
umns spaced  16  ft.  apart  carried  the  girder  system  shown  by 
Fig.  225,  which  in  turn  supported  a  3>^-in  floor  slab.  The 
walls  and  partitions  were  not  concrete.  The  following  records 
were  kept  by  the  authors : 


492 


CONCRETE    CONSTRUCTION. 


Forms.  —  The  column  forms  were  built  as  shown  by  Fig.  226. 
The  boards  were  i^2-in.  stuff,  surfaced  on  four  sides;  the 
yokes  were  spaced  2  ft.  apart.  The  I  x  6-in.  pieces  were  nailed 
to  the  2  x  4's  with  8-d.  nails  with  heads 
left  projecting  for  easy  pulling.  The 
girder  forms,  Fig.  227,  rested  on  the 
column  forms  and  on  intermediate 
posts  half-way  between  columns. 
These  intermediate  posts  were  3x4's 
with  4x4'xi2-in.  head  blocks  nailed 
to  their  tops  and  wedges  under  their 
bottoms.  The  girder  molds  were  i]/2- 
in.  stuff,  and  to  the  side  pieces  were 
nailed  i  x  4-in.  cleats  ;  the  bottom  and 
side  pieces  were  connected  by  ^  x  4-in. 
lag  screws  spaced  28  ins.  apart.  The 
floor  slab  stringers  were  carried  on  the 
i  x  4-in.  cleats  ;  they  were  spaced  28 
ins.  apart  and  were  not  nailed  ;  neither 
were  the  I  x  6-in.  lagging  boards  nailed 
to  the  stringers.  The  point  to  be  noted 


rTf  —  i 

i  *4  % 

-ff 

M 

T 

1 

"0 

ii 
n 

'  !V 

'-&* 

/    / 

*Ji' 

is  the  design  and  construction  of  the  Fig  226  —Column  Form  for 
forms  so  that    they  could  be    put  to- 

gether and  taken  apart  easily.    The  lumber  required  for  forms 
for  one  floor  91  x  112  ft.,  or,  say,  10,200  sq.  ft.,  was  as  follows: 

Lumber  for  columns,  ft.  B.  M  ..................  .......  9,000 

Lumber  for  lox  lo-in.  beams,  ft.  B.  M  ................  7,600 

Lumber  for  5  x  lo-in.  beams,  ft.  B.  M  ..................  2,700 

Intermediate  3  x  4-in.  posts,  ft.  B.  M  ...................  1,000 

Lagging,  i  x  6-in.  boards,  ft.  B.  M  ....................  .9,000 

Stringers,  3x4  ins.,  ft.  B.  M  ..........................  4>5°° 


Total  ft.   B.   M 


In  round  numbers,  we  can  say  that  34,000  ft.  B.  M.  of  lum- 
ber were  used  for  10,000  sq.  ft.  of  floor  area,  or  3.4  ft.  B.  M. 
per  i  sq.  ft.  Enough  forms  were  provided  to  erect  two  com- 
plete floors  ;  the  forms  for  the  lower  floor  being  removed  and 
erected  again  for  the  second  floor  above,  thus  using  all  the 


REINFORCED    CONCRETE    BUILDINGS. 


493 


lumber  three  times.  With  carpenters  at  $3.50  for  8  hours,  the 
forms  were  framed  ready  for  erection  for  $4  per  M.  ft.  B.  M. 
The  lumber  framed  ready  to  erect  cost  them : 

Lumber,  cost  per  M.  ft.  B.  M $26.00 

Labor,  framing  per  M.  ft.  B.  M 4.00 


Total  per  M.  ft.  B.  M $30.00 

Since  the  lumber  was  used  three  times,  $30-^-3  =  $10  is  the 
charge  against  each  1,000  ft.  B.  M.  needed  to  encase  the  con- 
crete on  a  floor.  There  were  nearly  34,000  ft.  B.  M.  per  floor, 
hence  the  cost  of  lumber  ready  for  erection  was  $340  per  floor. 
There  were  as  shown  below,  200  cu.  yds.  of  concrete  per  floor, 
so  that  the  cost  was  $340-^-200  =  $1.70  per  cu.  yd.  of  con- 
crete for  forms  ready  for  erection.  It  took  a  gang  of  5  men  7 


- 1  'xfLag  Screws.  £d  "CfoC 


Eng.-Confr 
Fig.    227.— Girder  and   Slab  Forms  for   6-Story   Building. 

days  to  tear  down  and  carry  up  the  forms  for  one  floor ;  hence 
5  X  $2  X  7  —  $70  per  floor,  or  practically  $2  per  M.  ft.  B.  M., 
or  $0.35  per  cu.  yd.  of  concrete  for  taking  down  and  carrying 
forms  two  stories.  It  took  a  gang  of  10  carpenters  7  days  to 
erect  these  forms,  which  at  $3.50  per  day  was  $245  per  floor, 
or  $7  per  M.  ft.  B.  M.,  or  $1.20  per  cu.  yd.  of  concrete. 

Concrete. — The  amount  of  concrete  per  floor  was  as  follows: 
Floor  slab  3^2  ins.  thick,  10,200  sq.  ft no  cu.  yds. 

Beams,  10  x  10  ins 40  cu  yds. 

Beams,    5x10   ins 20  cu.  yds. 

Columns,   15x15  ins.   (average) 30  cu.  yds. 


Total  concrete  per  floor 200  cu.  yds. 


494  CONCRETE    CONSTRUCTION. 

A  concrete  mixer,  a  hoist  and  a  gang  of  14  men  mixed  and 
placed  the  concrete  for  a  floor  in  7  days.  At  $2  per  day  for 
labor  this  gives  14  X  7  X  $2  =  $196,  or  say  $i  per  cu.  yd.  for 
mixing  and  placing  the  concrete. 


Reinforcement. — In  each  of  the  10  x  lo-in.  beams  there  were 
4,  i -in.  round  rods,  2  straight  and  2  bent,  and  stirrups  of  ^  x 
i-in.  straps  spaced  5  ins.  apart  at  columns  and  15  ins.  at  the 
center.  In  each  5  x  lo-in.  beam  there  was  half  as  much  steel 
as"  in  a  10  x  lo-in.  beam.  The  floor  slab  reinforcement  con- 
sisted of  54-in.  rods  spaced  5  ins.  apart  and  2  cross-rods  in  7- 
ft.  panel.  The  column  reinforcement  consisted  of  4  rods  aver- 
aging i  in.  in  diameter.  In  round  numbers  the  amount  of  steel 
required  for  each  floor  was,  therefore,  as  follows : 

Lbs.  steel  rods  in   10  x  zo-in.  beams 16,200 

Lbs.  steel  rods  in  5  x  lo-in.  beams 4,000 

Lbs.  stirrups  in  beams    3>ooo 

Lbs.  steel  rods  in  floor  slabs 3,8oo 

Lbs.  steel  rods  in  columns 1,400 


Total  pounds  steel  per  floor 28,400 

This  is  equivalent  to  142  Ibs.  of  steel  per  cubic  yard  of  con- 
crete, 'or  about  i  per  cent  of  the  total  volume  of  reinforced 
concrete  was  steel.  The  steel  in  the  beams  was  about  3  per 
cent.  It  required  a  gang  of  5  laborers  7  days  at  $2.25  per 
day,  to  bend  and  place  the  steel  for  each  floor  or  $86  for  labor 
on  28,400  Ibs.  of  steel.  This  is  equivalent  to  0.3  ct.  per  lb.,  or 
45  cts.  per  cu.  yd.  of  concrete. 

Summary  of  Costs. — Summarizing  the  figures  given  we  have 
the  following  cost  per  cubic  yard  of  concrete  in  floors  and 
columns : 


REINFORCED    CONCRETE    BUILDINGS.  495 

Per  cu.  yd. 

142  Ibs.  steel  at  2^  cts $  3.55 

I    bbl.    cement    2.50 

i  cu.  yd.  gravel i.io 

1/2  cu.  yd.  sand 0.55 

170  ft.  B.  M.  lumber  ready  to  erect  at  $10  (1-3  of  $30). .     1.70 

170  ft.  B.  M.  torn  down  at  $2 0.35 

170  ft.  B.  M.  erected  by  carpenters  at  $7 1.20 

Mixing1  and  placing  concrete   i.oo 

Shaping  and  placing  steel 0.45 

Superintendence 0.25 

Total    $12.65 

WALL  AND  ROOF  CONSTRUCTION  FOR  ONE- 
STORY  CAR  BARN. — The  barn  was  50  ft.  wide  and  190  ft. 
long,  divided  into  three  rooms  by  two  transverse  partitions 
and  covered  with  a  4-in.  roof  having  a  pitch,  of  y2  in.  per  foot. 
The  main  walls  were  12  ins.  thick  and  the  partition  walls  10 
ins.  thick.  The  main  room  no  ft.  long  had  four  car  tracks  its 
whole  length  with  pits  under  each  and  a  6-in.  reinforced  con- 
crete floor  slab  between.  The  floor  girders,  one  under  each 
rail,  were  12  ins.  square,  each  reinforced  by  three  i^-in.  rods, 
and  were  carried  on  I2xi2-in.  pillars.  The  total  yardage  of 
concrete  was  874  cu.  yds.  divided  as  follows : 

Walls  and  foundations,  cu.  yds 614 

Pillars  and  girders  in  track  pits,  cu.  yds 44 

Reinforced  floors,   cu.   yds 55 

Roof   160 

Total,  cu.  yds "873 

A  1-2^2-5  concrete  was  used  for  floors,  roof  and  girders  and 
a  1-3-6  concrete  for  foundations  and  walls.  There  were  26^ 
tons  of  reinforcing  steel,  or  61  Ibs.  per  cu.  yd.,  or  0.45  per  cent, 
of  the  volume  of  the  concrete  was  steel.  The  wages  paid 
were:  Foreman,  $2.50;  blacksmith,  $2 ;  engineer,  $1.75 ;  la- 
borers, $1.50;  two-horse  team  and  driver,  $3.67;  one-horse 
team  and  driver,  $2.92;  carpenter,  $2.25;  carpenters  worked 
9  hours ;  all  others  10  hours. 

Forms. — Carpenters  framed  and  erected  forms  and  common 
laborers  under  foreman  carpenter  took  them  down.  Lagging 
was  all  2-in.  stuff  and  uprights  3  x  4-in.  stuff.  Props  for  roof 


496  CONCRETE    CONSTRUCTION. 

forms  were  i8-ft.  round  timber  procured  on  the  job.  They 
were  6  ins.  in  diameter  at  the  top  and  cost  50  cts.  each,  91 
being  used.  These  props  are  not  included  in  the  lumber 
listed  below,  but  their  cost  is  included  in  the  costs  given. 
No  record  was  kept  of  the  number  of  times  the  lumber  was 
used,  but  as  54,643  ft.  B.  M.  were  bought  and  about  twice  this 
much  would  be  needed  to  enclose  the  concrete  if  used  only 
once,  we  will  assume  that  all  lumber  was  used  twice.  In- 
cluding the  props  there  were  about  60,000  ft.  B.  M.,  or  70  ft. 
B.  M.  per  cu.  yd.  of  concrete.  The  cost  of  the  lumber  was 
$1,520.86,  and  the  cost  of  labor  on  the  forms  was  $1,660.60,  so 
that  the  cost  of  forms  was : 

Item.  Per  cu.yd.     Per  M.  ft.     Per  sq.  ft. 

Lumber   $i-74  $13-5°  $0.038 

Labor    1.90  14.07  0.041 


Total  $3.64  $27.57  $0.079 

If  the  lumber  had  been  used  only  once  the  cost  per  cubic 
yard  would  have  been  $5.38,  and  per  M.  ft.  B.  M.,  $41.07. 

Concrete. — A  railway  track  was  run  the  full  length  of  the 
building  upon  what  Avas  eventually  the  fourth  track  of  the  car 
barn  and  a  Ransome  mixer  was  set  up  as  close  to  the  track  as 
possible  allowing  a  platform  to  be  built  between  it  and  the 
track.  Cars  were  brought  up  to  this  platform  and  the  ma- 
terials handled  by  wheelbarrows  direct  from  cars  to  mixer. 
Both  platform  and  mixer  were  moved  twice  as  the  work 
progressed.  The  concrete  was  taken  by  wheelbarrows  on  run- 
ways to  the  side  walls.  For  the  roof  it  was  hoisted  by  a  horse 
by  means  of  a  mast  having  an  arm  with  a  three-quarters 
swing;  the  barrows  were  hoisted  direct  using  a  hook  for  the 
wheel  and  two  rings  for  the  handles. 

The  cost  of  the  concrete  for  materials  was: 

I.I  bbl.  cement  at  $1.21,  per  cu.  yd $1-33 

y^  ton  sand  at  75  cts.,  per  cu.  yd 0.55 

Aggregate,  per  cu.  yd 0.88 

61  Ibs.  steel  at  1.9  cts.,  per  cu.  yd 1.15 

Lumber,  70  ft.  B.  M.  at  $27,  per  cu.  yd . . .  .    1.74 


Total  per  cu.  yd $5.65 


REINFORCED    CONCRETE    BUILDINGS.  497 

The  cost  of  labor  per  cubic  yard  was : 

Forms,  per  cu.  yd $1.900 

Mixing,  per  cu.  yd 0.210 

Placing,  per  cu.  yd 0,310 

Finishing,  per  cu.  yd 0.143 

Handling  cement,  per  cu.  yd 0.017 

Handling  sand,  per  cu.  yd 0.104 

Handling  steel,  per  cu.  yd 0.270 

Handling  aggregate,  per  cu.  yd 0.222 

Coal,  at  $4.25  per  ton,  per  cu.  yd o.oio 

Foreman,  per  cu.  yd 0.133 

Teams  and  laying  pipe  line,  per  cu.  yd 0.087 

Total,  per  cu.  yd $3406 

Summarizing,  we  have  the  following  cost  per  cubic  yard : 

Concrete  materials,  per  cu.  yd $2.76 

Labor  mixing  and  placing  concrete i.oi 

Forms,  materials  and  labor 3.64 

Reinforcement,  materials  and  labor 1.42 

Fuel,  foreman  and  pipe  line  labor 0.23 


Total,  per  cu.  yd $9.06 

The  cost  for  handling  steel,  making  stirrups,  welding,  etc., 
was  $8.90  per  ton,  or  0.45  ct.  per  Ib. 

CONSTRUCTING  WALL  COLUMNS  FOR  A  ONE- 
STORY  MACHINE  SHOP.— The  building  was  53  x  600  ft. ; 
each  side  wall  consisted  of  40  columns  of  channel  section  car- 
ried on  footings  of  channel  section  somewhat  heavier  than 
that  of  the  column.  The  columns  were  spaced  15  ft.  on  cen- 
ters and  each  was  7^  ft.  wide  so  that  there  were  7^-ft.  spaces 
between  columns,  which  were  filled  with  3-in.  curtain  walls 
extending  7^  ft.  above  the  floor.  Figures  228  and  229  show 
the  column  and  footing  construction.  Each  column  contained 
125  cu.  ft.,  or  4.63  cu.  yds.  of  1-3-5  I~m-  crushed  slag  con- 
crete above  the  footing  and  the  costs  given  here  relate  only  to 
the  columns  above  footings.  In  the  80  columns  there  were 
370  cu.  yds.  of  concrete. 


498 


CONCRETE    CONSTRUCTION. 


Forms. — A  column  form  is  shown  by  Fig.  230;  it  contains 
approximately  1,000  ft.  B.  M.  of  lumber.  Ten  of  these  forms 
were  used,  so  that  10,000  ft.  B.  M.  of  form  lumber  were  re- 
quired for  370  cu.  yds.  of  concrete,  or  27  ft.  B.  M.  per  cu.  yd. 
of  concrete.  Each  column  had  a  superficial  area  excluding 
ends  of  about  420  sq.  ft.,  so  that  420  X  80  =  33,600  sq.  ft.  was 
the  superficial  area  of  all  the  columns  and  10,000  ft.  B.  M.  -f- 


\-Groove  for 
-._  7'p". >j     /      I-Beam  Seats 


,-Koa  'from  Footing 


•^'Twisted  Bars 


tested 
tors; 


Fig.  228.— Channel  Section  Wall  Column  for  Factory  Building. 

33,600  sq.  ft.  =  0.3  ft.  B.  M.,  or,  say,  1-3  ft.  B.  M.,  of  form 
lumber  was  used  per  square  foot  of  concrete  enclosed.  The 
cost  of  the  forms  per  1,000  ft.  B.  M.,  and,  therefore,  per  form, 
was: 

Lumber,  1,000  ft.  B.  M.,  at  $31.75 $3I-75 

Labor  constructing  form 16.39 


Total  per  1,000  ft.  B.  M $48.14 


REINFORCED    CONCRETE    BUILDINGS. 


499 


This  gives  us  a  cost  per  cubic  yard  of  concrete  for  ma- 
terials and  labor  constructing  forms  of  $480-^-370  =  $1.30, 
and  per  square  foot  of  outside  wall  area  of  $480  -r-  (146  X  80) 
=  4.1  cts. 

The  erection  and  taking  down  of  the  forms,  owing  to  the 
weight  of  some  of  the  pieces,  was  done  by  means  of  special 
derricks.  The  footings  were  brought  to  within  l/2  in.  of  grade 
and  a  tenon  form  of  the  exact  shape  of  the  channel  section  of 
the  column  was  placed  on  top  and  filled  with  grout  to  a  depth 
of  I  in.  These  tenons  served  as  guides  in  setting  the  column 
forms,  and  proved  to  be  much  quicker  and  more  accurate  than 
points, 


Wall 


\ — " 


4K" 

/^.                

Ff< 

K 

l=JJjs=|^g=, 

4 

1 

jN/  ' 

fit-.        5<v,    ^Outline  a%\          ~S 
T^Tnlsted     Wall  Cols.  ^           T 
/  ?  Bar  ....-7'*"  ....                  ...\- 

i 

>    ^Curtain 
Wall 

i  —  » 

'                                      *               \ 

ffl 

?  - 

Uy,'H 

Plan. 

<-//- 

H 

j 

k 

<90  

^"Twisted  Bar 

| 

j 

DffftQffl  O/ 

<//» 

I         A 

.  ./ 

Vertical 
Section. 


X , 

Footing 

Front      Elevation. 
Fig.   229.— Footing  for  Wall  Column  Shown  by  Fig.  228. 

The  forms  were  assembled  on  the  ground  and  erected  by 
a  35~ft.  A-frame  derrick  mounted  on  wheels.  The  construction 
is  shown  by  Fig.  231.  This  derrick  had  a  capacity  of  about 

4  tons  and  carried  a  Ransome  friction  crab  hoist  driven  by  a 

5  h.p.  Meitz  &  Weiss  kerosene  oil  engine.     It  was  the  prac- 
tice to  set  a  number  of  forms  before  filling  any.    Thfs  enabled 
the  carpenter  gang  to  be  plumbing  up  the  first  form  while  the 
erecting  gang  were  setting  others.    The  forms  had  to  be  very 
securely  guyed  and  braced  to  withstand  the  impact  of  the  fall- 
ing concrete.     Very  little  trouble  was  had  in  keeping  them 
well  lined  up. 


5oo 


CONCRETE    CONSTRUCTION. 


Fig.   230.— Form   for  Molding  Wall   Column   Shown  by  Fig.   228. 


REINFORCED    CONCRETE    BUILDINGS. 


501 


Two  gangs  were  employed  in  assembling  forms  and  a  por- 
tion of  the  men  in  each  gang  also  shaped  and  placed  the  rein- 
forcement and  placed  and  tamped  the  concrete  in  the  forms 
so  that  no  exact  division  of  labor  is  possible.  The  organization 
of  these  gangs  and  the  wages  paid  were  as  follows : 

Derrick  Gang: 
i  foreman,  at  36  cts.  per  hour $  3.94 

1  crabman,  at  30  cts.  per  hour 2.70 

2  topmen,  at  27  cts.  per  hour 4.86 

2  bottom  men,  at  23  cts.  per  hour 4.14 

Total  per  9-hour  day $15.64 

Assembling  Gang: 

1  boss  carpenter,  at  47  cts.  per  hour $  4.23 

2  carpenters,  at  36  cts.  per  hour 6.48 

2  carpenters,  at  30  cts.  per  hour 5.40 

2  carpenters'  helpers,  at  25  cts.  per  hour 4.50 

4  men   forming   and   placing   reinforcing   steel   and   re- 
threading  bolts,  at  23  cts.  per  hour 8.28 

Total  per  9-hour  day $28.89 

Grand  total   $44-53 

These  gangs  assembled  and  erected  the  molds  and  con- 
creted 80  columns  in  22  working  days,  including  2  days  lost 
on  account  of  cold  weather,  so  that  4  columns  were  com- 
pleted per  day  of  9  hours.  We  can  subdivide  the  cost  as 
follows : 

Item.  Per  cu.  yd. 

Erecting  forms  and  concreting $0.81 

Assembling  forms  and  reinforcement 1.56 


Total  $2-37 

Charging  the  4  men  placing  reinforcement  and  rethreading 
bolts  to  forming  and  placing  reinforcement  alone  we  can 
figure  the  cost  of  fabrication  and  erection  of  reinforcement 
very  closely.  There  were  160  Ibs.  of  reinforcing  steel  in  each 
column,  hence  $8.28 -f-  (160  X  4)  =  i-3  cts.,  was  the  cost  per 
pound  of  forming  and  placing  it.  This  includes  handling. 


502 


CONCRETE    CONSTRUCTION. 


The  stripping  of  the  forms  was  carried  on  by  another  gang 
using  a  derrick  similar  to  the  first  one  described,  except  it 
could  be  of  lighter  construction  as  it  had  to  handle  only  the 
separate  parts  of  each  form  and  not  the  forms  assembled. 
The  derrick  shown  in  Fig.  232  was  a  33-ft.  A-frame,  with 
wheels  at  the  bottom  of  each  leg.  It  had  a  friction  crab  hoist 
driven  by  an  electric  motor,  both  of  which  were  fastened  to  the 
derrick  frame  between  the  shear  legs. 


X 


Plan. 


Eteva-Hon. 
Fig.  231.— Derrick  for  Erecting  Wall  Column  Forms  Shown  by  Fig.   230. 

The  operation  of  stripping  required  only  four  men  and  the 
crabman.  The  outside  flat  panel  was  removed  first,  and  left 
leaning  up  against  the  concrete  while  the  inside  trough 
shaped  panel  was  pried  loose  and  lowered  onto  the  ground 
with  its  inside  face  uppermost.  The  side  panels  being  com- 
paratively light,  were  stripped  without  the  use  of  the  derrick, 
and  these  panels  were  assembled  on  the  ground  with  the  inside 
piece.  The  derrick  then  picked  up  the  outside  panel  again, 
and  placed  it  in  its  proper  place.  After  the  bolts  were  put  in 
place,  the  assembled  form  was  nioved  on  rollers  to  another 


REINFORCED    CONCRETE    BUILDINGS. 


503 


point  in  the  line  of  columns  where  it  was  again  erected.  The 
arrangement  of  derricks  for  erecting  and  stripping  forms  is 
shown  in  Fig.  233. 

The  gang  stripping  forms  was  made  up  as  follows : 

I  foreman,  at  30  cts.  per  hour $  2.70 

i   crabman,  at  27  cts.  per  hour 2.43 

1  topman,  at  27  cts.  per  hour 2.43 

2  bottom  men,  at  23  cts.  per  hour 4.14 

Total  per  9-hour  day $11.70 


H  K 50'0"- — H 

Fig.   232.— Derrick  for  Stripping  Wall  Column  Forms  Shown  by  Fig.   230. 

This  gang  of  five  men  stripped  4  columns  containing  18.52 
cu.  yds.  of  concrete  each  day,  so  that  the  cost  of  stripping 
was  $11.70-^-18.52  —  62.7  cts.  per  cu.  yd. 

Concrete. — The  concrete  was  mixed  in  a  No.  2  Ransome 
mixer  and  delivered  to  the  work  in  Ransome  concrete  carts. 
These  carts  w^re  pushed  along  a  runway  which  terminated 
in  a  slight  incline  under  the  derrick  so  that  their  contents 
could  be  emptied  into  the  derrick  buckets. 

The  concrete  was  hoisted  in  an  8-ft.  bottom  dump  bucket, 
using  the  derrick  described  above.  It  was  necessary  to  stir  up 
the  concrete  thoroughly  with  long-handled  slicers  as  it  was 
being  deposited  in  order  to  prevent  segregation.  This  expedi- 
ent combined  with  a  wet  mixture  and  tight  molds  was  found 
to  overcome  this  difficulty  very  effectually. 


504 


CONCRETE    CONSTRUCTION. 


The  gang  mixing  and  wheeling  concrete  was  made  up  as 
follows  : 
i  mixer  foreman  and  engineer  at  27  cts.  per  hour  .......  $  2.43 

4  laborers  charging  mixer  at  18  cts  per  hour  ...........     6.48 

4  laborers  wheeling  concrete  at  18  cts.  per  hour  .......     6.48 

Total  per  p-hour  day  ..........................  $!5-39 

This  gang  mixed  and  wheeled  concrete  for  four  columns, 

or  18.52  cu.  yds.,  hence  the  cost  per  cubic  yard  was  82.6  cts. 
With  cement  at  $1.60  per  bbl.,  sand  at  $i  per  cu.  yd.  and 

slag  at  $1.10  per  cu.  yd.  the  cost  of  materials  per  cubic  yard 

of  concrete  was  $3. 


Cb/umn 


/runway  for  Loaded  Carfs 


Derrick  for 
Stripping  Forms 


toy 


Perr/ck  for  £  -ecting 
Forms  and  Hoi$+ingr 
Concrete 


Wire  Rope 


Fig.   233. — Arrangement  of  Derricks   for    Erecting    and    Stripping   Forms. 

Summarizing  the  above  figures  we  have  the  following  cost 
per  cubic  yard  of  concrete  in  place: 

Item.  Per  cu.  yd. 

Concrete   materials $3.00 

Reinforcing  steel   0.73 

Forms,  lumber  and  framing 1.30 

Forms,  erecting  and  concreting 0.81 

Forms,  assembling  and  reinforcement 1.56 

Forms,  stripping   0.63 

Mixing  and  wheeling  concrete 0.83 

Total $&86 


REINFORCED    CONCRETE    BUILDINGS. 


505 


CONSTRUCTING  ONE-STORY  WALLS  WITH  MOV- 
ABLE FORMS  AND  GALLOWS  FRAMES.— In  construct- 
ing the  walls  for  an  85  x  3O-ft.  factory  building  at  Old  Bridge, 
N.  J.,  Mr.  A.  E.  Budell  made  use  of  movable  forms  and  gal- 
lows frames  to  construct  the  curtain  walls  and  columns  in 
one  piece.  Each  side  wall  was  built  its  full  height  in  suc- 
cessive 5o-ft.  lengths  by  depositing  the  concrete  between  two 
forms  which  were  moved  upward  as  the  concreting  pro- 
gressed. .  Fig.  234  indicates  'the  mode  of  procedure.  The 
form  was  raised  and  lowered  by  means  of  two  gallows  frames 
fitted  with  blocks  and  tackle.  A  steel  cable,  with  a  trolley 


'Sub-silk 


Fig     234.— Gallows    Frame     Supporting    Wall    Form    Panels    for    One-Story 

Building. . 

affixed,  extending  from  one  frame  to  the  other,  provided  a 
convenient  mode  of  hoisting  material  to  the  form,  and  the 
gallows  frames  took  the  place  of  ladders  for  climbing  onto  the 
structure.  No  scaffolding  whatever  was  used  and  only  one 
man  was  required  overhead  to  dump  the  buckets  and  tamp 
the  concrete  into  place. 

The  two  walls  were  carried  up  simultaneously,  one  form 
being  shifted  into  place  and  filled  while  the  other  was  left  in 
place  until  the  concrete  was  sufficiently  hard.  It  was  found 
that  18  hours  was  amply  sufficient  to  allow  the  concrete  to  set 


506 


CONCRETE    CONSTRUCTION. 


hard,  after  which  the  form  was  removed  and  lifted  to  a  higher 
level.  Thus  the  men  were  continuously  engaged  in  lifting 
and  rilling  first  one  form  and  then  the  other.  The  average 


-3 


ll 


Fig.    235. — Details   of   Wall   Form    Panel    for 

length  of  time  required  to  remove,  raise 
5  to  6  hours.  Thus,  two  forms  could 
almost  every  day.  The  construction  of 


One-Story  Building. 

and  fill  one  form  was 

be  raised  and   filled 

the  forms  and  of  the 


REINFORCED    CONCRETE    BUILDINGS.  507 

gallows  frames  is  shown  by   Figs.  234  and  235.     The  cost 
of  one  set  of  forms  and  gallows  frames  was  as  follows: 

320  ft.  B.  M.  of  2  x  10  in.  x  10  ft.  plank  at  $34 $  10.88 

150  ft.  B.  M.  of  3  x  4  in.  x  16  ft.  spruce  at  $33 :  5.25 

135^  ft.  B.  M.  i  x  8  in.  yellow  pine  at  $30 4.08 

335  ft.  B.  M.  1^4  x6in.  spruce  at  $33 11.05 

4  posts  6  x  8  in.  x  26  ft.  =  416  ft.  B.  M.  at  $30 12.48 

4  sills  6x8  ins.  x  16  ft.,  2  caps  6x6  ins.  x  9  ft.,  4  braces 

6x6  ins.  x  16  ft.  =  490  ft.  B.  M.  at  $30 ;     14.70 

3  pieces  3  x  10  ins.  x  20  ft.  —  150  ft.  B.  M.  at  $30 4.50 


Total  lumber  (1.996.5  ft.  B.  M.) $  62.94 

Accessories : 

Bolts  for  trussing,  675  Ibs.  at  2  cts $  I3-5O 

Iron  guy  rope  and  clips 7.00 

Blocks 8.00 

One  coil  of  %-in.  rope 28.00 


Total  accessories   $  56.50 

Labor  making  one  outfit : 
2  men,  8  days,  at  $2.75  per  9  hrs $  44.00 


Grand  total $163.44 

This  sum  covered  the  cost  of  forms  for  one  side  of  the  build- 
ing 85  ft.  long  and  containing  150  cu.  yds.  of  concrete,  hence 
the  cost  of  forms  was  in  round  figures  $1.10  per  cu.  yd.  of 
concrete.  Each  cubic  yard  of  concrete  required  1,997-1-  150  = 
13  1-3  ft.  B.  M.  of  form  lumber. 

The  concrete  was  a  1-2^-4^  mixture.  A  careful  record  for 
15  days,  showed  an  average  of  2.8  cu.  yds.  of  concrete  placed 
in  6  hours  by  a  gang  of  6.3  men.  From  this  we  can  figure  the 
cost  of  concrete  in  place  to  be  about  as  follows: 

2.8  cu.  yds.  concrete  at  $3  for  materials $  8.40 

6.3  men  6  hours  at  1 5  cts 5.67 

i  foreman  6  hours  at  $4  per  day 2.00 

Total  per  cu.  yd $16.07 


x 

OF  THE  X 

UNIVERSITY    J 

OF  / 

/ 


508 


CONCRETE    CONSTRUCTION. 


Thus  the  cost  of  concrete  in  place  was  $16.07-^2.8  — $5.73 
per  cu.  yd.  Adding  the  cost  of  forms  we  get  $5.73  +  $1.10  = 
$6.83  per  cu.  yd.  as  the  cost  for  labor  and  materials  in  con- 
structing forms  and  mixing  and  placing  concrete. 

Offsets  and  molding  decorations  were  easily  made,  although 
they  were  quite  numerous  on  the  building  in  question,  at 
least  more  so  than  would  ordinarily  be  the  case  in  mill  build- 
ing construction.  The  offset  of  I  ft.  at  every  column  was 


Fig.   236. — Detail  of  Column  and  Cantilever  Column   Footing  for  Four-Story 

Garage. 

made  very  readily  by  sliding  wooden  shoulder  pieces  into  place 
on  the  inner  face  of  the  form,  which  pieces  in  turn  received 
2-in.  faced  planking,  the  latter  being  slid  into  place  from  above. 
Thus  the  entire  system  was  collapsible  and  small  alterations 
were  easily  made  whenever  the  form  was  shifted.  Flat  sur- 
faces or  offsets  could  be  obtained  at  will  by  either  removing 
or  setting  in  the  shoulder  pieces.  Molding  effects  were  made 
on  the  front  face  of  the  wall  by  tacking  molding  strips  to  the 


REINFORCED    CONCRETE    BUILDINGS. 


509 


form  wherever  necessary.  The  entire  work  was  done  with 
common  labor  and  the  finished  building  presented  a  smooth, 
homogeneous  surface  which  required  very  little  dressing. 

FLOOR  AND   ROOF   CONSTRUCTION  FOR  FOUR- 
STORY  GARAGE.— The   building  was    53x200   ft.,   and   4 


k-/8' 
Section  LrL 


SecttonM-M. 


Fig.   237. — Details  of  Cantilever  Girders  for  Mezzanine  Floor  for  Four-Story 

Garage. 

stories  high,  with  provision  for  2  additional  stories  in  the  de- 
sign of  footings  and  columns.  Two  rows  of  wall  columns  con- 
nected by  transverse  girders  carrying  the  floor  and  roof 
slabs  made  a  comparatively  simple  construction,  except  for  a 
mezzanine  floor  carried  on  cantilever  beams  and  except  for  the 


510  CONCRETE    CONSTRUCTION. 

use  of  cantilever  footings;  these  two  special  details  are  shown 
by  Figs.  236  and  237.  The  amount  of  concrete  in  the  building 
was  1,910  cu.  yds.,  distributed  as  follows: 

Cu.  yds. 

Footings,  reinforced   190 

Columns,  reinforced . .  . . 450 

Floors  and  roof,  reinforced 1,100 

Floor  on  ground,  not  reinforced   170 

Total    1,910 

The  amount  of  reinforcing  metal  used  was  237  tons,  distrib- 
uted as  follows :  " 

Item.  Tons.  Lbs.  per  cu.  yd. 

Footings 42  442 

Columns    20  90 

Floors  and  roof 175  318 


Total  and  average 237  272 

This  is  equivalent  to  2  per  cent,  of  steel  in  1,910 — 170=1 
1,740  cu.  yds. 

Forms. — The  total  area  of  concrete  covered  by  forms  (1,740 
cu.  yds.)  was  94,000  sq.  ft.,  distributed  as  follows: 

Footings,  sq.  ft 4,000 

Columns,  sq.  ft 20,000 

Floors  and  girders,  sq.  ft 70,000 

Total,  sq.  ft 94,000 

For  the  work  50,000  ft.  B.  M.  of  old  lumber  was  used  and 
170,000  ft.  B.  M.  of  new  lumber  was  bought,  the  cost  being  as 
follows : 

50  M.  ft.  B.  M.  at  $13  per  M $   650 

170  M.  ft.  B.  M.  at  $26  per  M 4,420 

220  M.  ft.  B.  M.  at  $23 $5,070 

This  is  equivalent  to  126  ft.  B.  M.  per  cu.  yd.  of  concrete. 
New  forms  were  made  for  each  floor  except  the  sides  of  the 
girder  molds  which  were  re-used  so  far  as  they  would  fit, 
but  the  roof  forms  were  made  from  lumber  used  for  the  floors. 


REINFORCED    CONCRETE    BUILDINGS. 


511 


In  all  no  more  than  20  per  cent,  of  the  form  lumber  was  used 
a  second  time.  In  round  figures  new  lumber  was  required  for 
80,000  sq.  ft.  of  concrete ;  this  gives  a  cost  for  lumber  of  6.4 
cts.  per  sq.  ft.  The  construction  of  the  column  and  floor 
forms  is  shown  by  Fig.  238.  A  force  of  15  carpenters  at  $4.40 
per  day  under  a  foreman  at  $35  per  week  erected  and  tore 
down  forms;  the  carrying  was  done  by  laborers  at  $1.70  per 
day  working  under  a  foreman  at  $35  per  week;  carpenters 
worked  an  8-hour  and  laborers  a  lo-hour  day.  Forms  for  one 
floor  were  framed  and  erected  in  8  to  10  days.  The  cost  of 
forms  for  1,740  cu.  yds.  and  80,000  sq.  ft.  of  concrete  and  per 
M.  ft.  B.  M.  was  as  follows: 


Enq.-Confr. 


]    r~ 

- 

... 

i     ] 

j      ! 

- 

t'Pkmlrs 

<— 

Ow 

~Ba> 

LJ_ 

* 

: 

\    \ 

- 

I'D 


Fig.    238.— Column   and   Floor  Forms  for   Four-Story   Garage. 

Item.  Percu.  yd.     Per  sq.  ft.     Per  M.  ft. 


Lumber $2.90 

Framing,  erecting  and  removing.  2.00 
Handling  lumber i.io 


$0.064 
0.057 


$23.00 

I5-67 
8.70 


Totals   $6.00  $0.121  $47-37 

The  lumber  had  a  considerable  salvage  value  which  'is  not 
allowed  for  in  the  above  figures. 


512  CONCRETE    CONSTRUCTION. 

Concrete. — The  concrete  was  a  Portland  cement,  ^4  -in.  trap 
rock  mixture,  mixed  wet  in  two  Chicago  Improved  Cube 
Mixers  equipped  with  charging  buckets.  The  mixers  were 
located  on  the  ground  floor,  one  at  the  rear  and  one  at  the 
front  of  the  building,  both  discharging  directly  to  a  hoist. 
With  a  gang  of  30  men  at  $1.70  per  ro-hour  day  under  a  fore- 
man at  $35  per  week  a  floor  was  concreted  in  2  days,  the 
columns  being  concreted  the  first  day  and  the  floor  being 
concreted  the  second  day.  The  labor  cost  for  mixing  and 
placing  concrete  and  for  fabricating  and  setting  reinforcement 
was  as  follows: 

Item.  Per  cu.  yd. 

Mixing  and   placing  concrete $1-95 

Erecting  and  setting  steel ........   2.05 

Total $4.00 

The  cost  of  concreting  includes  the  cost  of  granolithic  sur- 
face for  the  floor  slabs.  The  girder  reinforcement  was  made 
up  into  unit  frames  and  the  frames  were  set  as  a  unit,  horses 
set  over  the  molds  being  used  to  suspend  and  lower  them 
into  place.  The  cost  of  $2.05  per  cu.  yd.  is  equivalent  to  ^4  ct. 
per  Ib.  Summarizing,  we  have  the  following  cost  for  ma- 
terials and  labor  on  forms  and  for  labor  mixing  and  placing 
concrete  and  reinforcement: 

Per  cu.  yd. 

Lumber  for  forms $  2.90 

Labor  on  forms 3.10 

Labor  on  concrete i  .95 

Labor  on  steel 2.05 

Total  $10.00 

This  $10  total  does  not  include  the  cost  'of  the  concrete  nor 
of  the  steel. 


CHAPTER    XX. 

METHOD  AND  COST  OF  BUILDING  CONSTRUCTION 
OF  SEPARATELY  MOLDED  MEMBERS. 

This  chapter  deals  exclusively  with  the  methods  and  cost 
of  molding  and  erecting  separately  molded  wall  blocks,  girders, 
columns  and  slabs.  The  structural  advantages  and  disad- 
vantages of  this  type  of  construction  as  compared  with  mono- 
lithic construction  will  not  be  considered.  The  data  given 
in  succeeding  paragraphs  show  how  separate  piece  work  has 
been  done  and  what  it  has  actually  cost  to  do  it  in  a  number 
of  instances. 

COLUMN,  GIRDER  AND  SLAB  CONSTRUCTION.— 

European  engineers  have  developed  several  styles  of  open  web 
or  hollow  girder  and  column  shapes,  but  in  America  solid 
columns  and  girders  have  been  used  except  in  the  compara- 
tively few  cases  where  one  of  the  European  constructions  has 
been  introduced  by  its  American  agents. 

Warehouses,  Brooklyn,  N.  Y. — In  constructing  a  series  of 
warehouses  in  Brooklyn,  N.  Y.,  the  columns  and  girders  were 
molded  in  forms  on  the  ground.  For  molding  the  column^, 
forms  consisting  of  two  side  pieces  and  one  bottom  piece,  were 
used,  saving  25  per  cent,  in  the  amount  of  lumber  required  for  a 
column  form,  and  doing  away  with  yokes  and  bolts,  since  only 
simple  braces  were  required  to  hold  the  side  forms  in  place. 
It  was  found  that  the  side  forms  could  readily  be  removed  in 
24  to  48  hours,  thus  considerably  reducing  the  time  that  a 
considerable  portion  of  the  form  lumber  was  tied  up.  It  was 
figured  by  Mr.  E.  P.  Goodrich,  the  engineer  in  charge  of  this 
work,  that  this  possible  re-use  of  form  lumber  reduced  the 
amount  required  another  50  per  cent,  as  compared  with  mold- 
ing in  place.  Girders  were  molded  like  columns  in  three-sided 
forms;  the  saving  in  form  work  was  somewhat  less  than  in 
the  case  of  columns,  but  it  was  material.  In  general,  Mr. 
Goodrich  states,  the  cost  of  hoisting  and  placing  molded  con- 

513 


514 


CONCRETE    CONSTRUCTION. 


crete  members  is  higher  per  yard  than  when  the  concrete  is 
placed  wet.     That  is  in  mass  before  it  is  hardened. 

Factory,  Reading,  Pa. — In  constructing  a  factory  at  Read- 
ing, Pa.,  an  open  or  lattice  web  type  of  girder  invented  by  Mr. 
Franz  Visintini  and  extensively  used  in  Austria  was  adopted ; 
columns  were  molded  in  place  in  the  usual  manner  with  bracket 
tops  to  form  girder  seats.  The  girders  were  reinforced  with 
three  trusses  made  up  of  top  and  bottom  chord  rods  connected 
by  diagonal  web  rods;  one  truss  was  located  at  the  center  of 
the  beam  and  one  at  each  side.  The  method  of  molding  was 
as  follows :  The  trusses  were  made  by  cutting  the  chord  rods 
to  length  and  threading  the  web  diagonals  and  verticals  onto 
.them.  To  permit  threading  the  web  pieces  were  bent,  when 
rods  were  used,  with  an  eye  at  each  end ;  when  straps  were 
used  the  ends  were  punched  with  holes.  The  work  was  very 
simple  and  was  done  mostly  by  boys  in  the  machine  shop  of 


Fig.    239. — Sketch    Showing   Forms    and   Reinforcement   for   Visintini    Girder. 

the  company  for  which  the  building  was  being  erected.  The 
girders  were  molded  two  at  a  time  in  forms  constructed  as 
shown  by  the  sketch.  Fig.  239.  A  form  consisted  of  a  center 
board,  two  side  boards,  two  end  pieces  and  the  proper  number 
of  cast  iron  cores,  all  clamped  together  by  three  yokes.  Tri- 
angular cast  iron  plates,  A,  were  screwed  to  the  bottom  boards 
for  spacers.  The  side,  center  and  end  boards  were  then  set 
up  and  the  end  clamps  were  placed.  The  cast  iron  hollow 
cores,  B,  were  then  set  over  the  spacers,  and  the  form  was 
ready  for  pouring.  A  layer  of  concrete  was  placed  in  the 
bottom  of  the  mold  and  the  first  side  truss  was  placed;  the 
concrete  was  then  brought  half  way  up  and  the  middle  truss 
was  placed ;  concreting  was  then  continued  up  to  the  plane 
of  the  second  side  truss  which  was  placed  and  covered.  Cores 
and  forms  were  all  cleaned  and  greased  each  time  they  were 


SEPARATELY    MOLDED    PtECE    BUILDINGS. 


515 


used.  The  cores  were  removed  first  by  means  of  a  lever 
device  and  generally  within  three  or  four  hours  after  the  con- 
crete was  placed.  The  remainder  of  the  form  was  taken  down 
in  two  to  four  days  and  the  beam  removed. 

Kilnhouse,  New  Village,  N.  J.— In  constructing  a  kiln  house 
for  a  cement  works  one  story  columns  with  bracket  tops  and 
5o-ft.  span  roof  girders  were  molded  on  the  ground  and  erected 
as  single  pieces.  The  columns  by  rough  calculation  averaged 
about  2  cu.  yds.  of  concrete  and  675  Ibs.  of  reinforcement  each 
or  about  337  Ibs.  of  steel  per  cubic  yard.  The  girders  aver- 
aged by  similar  calculation  5  cu.  yds.  of  concrete  and  2,260 


Fig.  240. — Arrangement  for  Molding  Ten  Single-Bracket  Columns. 

Ib's.  of  steel,  or  452  Ibs.  per  cubic  yard  of  concrete.  The  aver- 
age weight  of  columns  was  thus  not  far  from  4  1-3  tons  and  of 
girders  fully  n  tons. 

Several  combinations  of  arrangements  were  used  for  mold- 
ing the  columns  and  girders.  For  wall  columns  having  one 
bracket  the  arrangement  shown  by  Fig.'  240  was  adopted. 
The  concrete  slab  molding  platform  was  covered  with  paper, 
and  on  this  the  two  outside  and  the  middle  columns  were 
cast  in  forms.  When  those  columns  had  set  the  forms  were 
removed,  the  intervening  spaces  were  papered  and  the  two  re- 
maining columns  were  cast.  Ten  columns,  five  sets  of  two 
columns  in  line,  were  cast  on  each  base.  The  remaining  col- 


CONCRETE    CONSTRUCTION. 


umns  were  cast  in  combination  with  girders  as  shown  by  Fig. 
241.  The  two  outside  lines  of  columns  (i)  were  molded  in 
forms,  allowed  to  stand  until  set  and  then  stripped.  Using  a 
column  surmounted  by  a  shallow  side  form  for  one  side  and 
a  full  depth  side  form  for  the  other  side  molds  were  fashioned 


Fig.   241.— Arrangement  for  Molding  Four  Four-Bracket   Columns   and   Four 

Roof  Girders. 

for  the  two  outside  girders,  Nos.  2  and  3.  One  full  depth  side 
form  and  the  side  of  girder  No.  2  formed  the  mold  for  girder 
No.  4.  Girder  No.  5  was  then  molded  between  girders  No.  3 
and  No.  4. 


Enq-Contr: 


Fig.    242.—  Forms    for    50-ft.    Roof   Girders. 


The  construction  of  the  girder  forms  is  shown  by  Fig.  242. 
This  drawing  shows  one  of  the  four  main  sections  making  up 
a  complete  form.  A  full  size  form  of  this  construction  con- 
tained about  1,100  ft.  B.  M.  of  lumber,  and  three  were  built, 
so  that  3,300  ft.  B.  M.  of  form  lumber  were  used  for  molding 
20  girders,  or  33  ft.  B.  M:  per  cubic  yard  of  concrete.  A  full 


SEPARATELY    MOLDED    PIECE    BUILDINGS. 

size  column  form  contained  about  225  ft.  B.  M.  of  lumber,  and 
eight  were  constructed,  so  that  1,800  ft.  B.  M.  of  form  lumber 
were  used  for  molding  56  columns,  or  about  16  ft.  B.  M.  per 
cubic  yard  of  concrete. 

The  following  was  the  cost  of  erecting  a  full  column  form 
including  lining,  plumbing,  bracing  and  yoking,  but  excluding 
lumber  and  original  construction  : 

i   carpenter,  3  hrs.,  at  $0.25 $0.750 

i   helper,  3  hrs.,  at  $0.175 0.525 

1  helper,  i  hr.,  at  $0.175 0.175 

1-5  boss  carpenter,  3  hrs.,  at  $0.30 0.180 

Total  $1.630 

This  gives  a  cost  of  $7.25  per  M.  ft.  B.  M.  for  erecting  col- 
umn forms. 

The  cost  of  erecting  a  full  size  girder  form  including  lining, 
plumbing,  bracing  and  setting  six  bolts  was  as  follows : 

2  carpenters,  5  hrs.,  at  $0.25      $2.50 

2  helpers,  5  hrs.,  at  $0.175 1-75 

2  laborers,  */2  hr..,  at  $0.15 , 0.15 

14  boss  carpenter,  at  $0.30 0.375 

Total    $4-775 

This  gives  a  cost  of  $4.35  per  M.  ft.  B.  M.  for  erecting  girder 

forms. 

The  reinforcement  was   erected  inside  the  forms  for  both 

columns  and  girders.     The  cost  of  erection  for  one  column 

was : 

2  laborers,  4  hrs.,  at  $0.15 $I-2° 

1-3  foreman,  4  hrs.,  at  $0.225 0.30 

Total  fr-SO 

This  gives  a  cost  of  about  0.22  cts.  per  pound  for  erecting 
column  reinforcement,  including  the  bending  of  the  horizontal 
ties  or  hoops.  The  girder  reinforcement  was  erected  by 
piece  work  at  a  cost  of  $1.80  per  girder— or  about  0.08  ct.  per 
pound. 


518  CONCRETE    CONSTRUCTION. 

The  concrete  used  was  a  1-6  mixture  of  Portland  cement 
and  crusher  run  stone  all  passing,  a  y2-m.  sieve  and  10  per  cent, 
passing  a  200  mesh  sieve.  No  trouble  was  had  in  handling 
this  fine  aggregate.  It  was  mixed  in  a  Ransome  mixer,  ele- 
vated so  as  to  deliver  the  batches  into  cars  on  a  standard 
gage  track.  This  track  ran  between  the  base  slabs  on  which 
the  molding  was  done.  Each  car  held  about  3  cu.  yds.  and 
discharged  through  a  side  gate  and  spout  directly  into  the 
forms,  the  mixture  being  made  so  wet  that  it  would  flow 
readily.  The  company  used  its  own  cement  and  stone  for  con- 
crete and  charged  up  the  cement  at  $i  per  barrel  and  the  stone 
at  60  cts.  per  cubic  yard.  At  these  prices,  and  assuming  that 
a  cubic  yard  of  concrete  of  the  mixture  above  described  would 
contain  about  1.25  bbl.  of  cement  and  1.5  cu.  yd.  of  stone,  we 
have  the  following  cost  of  materials  per  cubic  yard  of 
concrete : 

1.25  bbls.  of  cement,  at  $i $1*25 

1.5  cu.  yds.  stone,  at  $0.60 0.90 


Total $2.15 

The  actual  cost  of  mixing  the  concrete  and  delivering  it  to 
the  cars  was  as  follows : 

Item.  Per  cu.  yd. 

i  foreman,  at  20  cts  per  hour.  .  . $0.0300 

3  man  shoveling  stone,  at  15  cts.  per  hour 0.0675 

3  men  filling  hopper,  at  15  cts.  per  hour 0.0675 

I  man  bringing  cement,  at  18  cts.  per  hour. .".-.' 0.0225 

i  man  dumping  cement,  at  15  cts.  per  hour 0.0225 

9  h.p.;  at  l/2  ct.  per  h.p.  hour 0.0450 

Superintendence,   repairs,   etc 0.0270 

Total    .- $0.2820 

The  cost  of  hauling  the  concrete  from  mixer  to  forms  ran 
about  2.7  cts.  per  cubic  yard,  so  that  we  have  a  cost  for  con- 
crete in  place  of: 

Concrete  materials,  per  cu.  yd $2.150 

Mixing  concrete,  per  cu.  yd 0.281 

Hauling  concrete,  per  cu.  yd 0.027 

Total  cost,  per  cu.  yd $2.458 


SEPARATELY    MOLDED    PIECE    BUILDINGS. 


519 


The  cost,  then,  per  column  or   girder  molded,  assuming  that 
it  was  necessary  to  erect  a  full  form,  was  about  as  follows : 

Columns: 

2  cu.  yds.  concrete,  at  $2.46 .....$  4.92 

675  Ibs.  steel,  at  zl/2   cts. ...... 16.77 

Erecting  steel,  at  0.22  ct.  per  Ib 1.50 

Erecting  forms 1.63 

Total  $24.82 


Fig.  243.— View  Showing-  Method  of  Hoisting  Molded  Columns. 

Girders : 

5  cu.  yds.  concrete,  at  $2.46. . $12.30 

2,260  Ibs.  steel,  at  2l/2  cts 56-5° 

Erecting  steel,  at  0.08  ct.  per  Ib. 1.80 

Erecting  forms  4-77 

Total    $75-37 

These   figures  give  a  unit  cost  of  $12.41   per  cu.  yd.  for 
molded  columns,  and  of  $15.07  per  cu.  yd.  for  molded  girders. 


520  CONCRETE    CONSTRUCTION. 

The  columns  were  erected  by  a  Browning  locomotive  crane, 
which  lifted  and  carried  them  to  the  work  and  up-ended  them 
into  place.  To  facilitate  lifting  the  columns  from  the  mold- 
ing bed  a  i^-in.  pipe  8  ins.  long  was  cast  into  both  ends; 
pins  inserted  into  these  sockets  provided  hitches  for  the  tackle. 
The  column  was  lifted  off  the  molding  bed  and  blocked 
up,  then  iron  clamps  were  attached,  one  at  each  end,  as  shown 
by  Fig.  243.  A  gang  of  I  foreman  and  14  men  erected  from 
5  to  7,  or  an  average  of  6  columns  per  lo-hour  day.  The 
average  wages  of  the  erecting  gang  were  21  cts.  per  hour.  The 
cost  then  of  column  erection  was  (14  X  $2.10)  -j-6  =  $5.25 
per  column,  or  $2.63  per  cu.  yd.  of  concrete. 

The  roof  girders  had  i-in.  eye-bolts  24  ins.  long  cast  into 
them  vertically  about  4  ft.  from  the  ends.  They  were  lifted 


i»Rope 


SO'O" 


Fig.  244.— Sketch  Showing  Sling  for  Erecting  50-ft.  Roof  Girders. 

off  the  molding  bed  by  tackle  by  the  locomotive  crane  to  these 
eye-bolts  and  blocked  up  to  permit  the  adjustment  of  the 
sling.  This  sling  is  shown  by  the  sketch,  Fig.  244,  and  as  will 
be  observed  acts  as  a  truss.  At  first  it  was  used  without  the 
vertical,  but  the  cantilever  action  of  the  unsupported  ends 
caused  cracks.  The  girders  were  loaded  onto  cars  by  the  loco- 
motive crane  and  taken  to  the  work,  where  they  were  hoisted 
and  placed  by  a  gin  pole.  The  girder  erecting  gang  consisted 
of  i  foreman  and  14  men,  working  a  lo-hour  day  at  21  cts. 
per  hour.  This  gang  erected  four  girders  per  day,  at  a  cost 
of  (15  X  $2.10)  -=-4  =  $7.87  per  girder,  or  $1.57  per  cu.  yd. 

of  concrete. 
/ 

The  cost  of  girders  and  columns  in  place  was  thus  about  as 
follows : 


SEPARATELY    MOLDED    PIECE    BUILDINGS. 


521 


Columns :  Per  unit.  Per  cu.  yd. 

Molding    $25.00  $12.50 

Erecting 5.25  2.63 

Totals $30.25  $15.13 

Girders : 

Molding   $75-00  $15.00 

Erecting  7.87  1.57 

Totals   $82.87  $16.57 


Fig.  245.— View  Showing  Method  of  Handling  Roof  Slabs. 

In  this  same  building  the  roof  was  composed  of  12  x  6*4  ft.  x 
4-in.  slabs  molded  in  tiers ;  a  slab  was  molded  and  when  hard 
was  carpeted  with  paper  and  the  form  moved  up  and  a  second 
slab  molded  on  top  of  the  first.  This  operation  was  repeated 
until  a  tier  of  slabs  had  been  molded.  By  molding  each  slab 
with  a  3-in.  overlap,  as  shown  by  Fig.  245,  they  could  be 
easily  separated  by  lifting  on  hooks  inserted  under  the  over- 
hanging ends.  Each  slab  contained  0.925  cu.  yd.  of  concrete 
and  about  116^  Ibs.  of  reinforcement.  The  cost  of  molding 
one  roof  slab,  including  materials,  forms  and  labor,  was  as 
follows : 


522 


CONCRETE    CONSTRUCTION. 


Materials :                                                Per  slab.  Per  cu.  yd. 

i  bbl.  cement,  at  $i $1.000  $1.081 

1. 06  tons  stone,  at  $0.60 0.636  0.687 

n6^4  Ibs.  steel,  at  2%  cts 2.647  2.862 

Total    $4.283  $4.630 

Forms : 

Lumber  and  making .• $0.104  $0.112 

92  sq.  ft.  paper,  at  33   1-3  cts.  per  500 

sq.  ft 0.055  0.059 

Labor  erecting  and  removing 0.5625  0.608 

Total $0.7215  $0.779 

Mixing,  Hauling  and  Placing: 

Mixing $0.222  $0.240 

Hauling 0.025  0.027 

Placing  concrete  and  steel. 0.170  0.183 

Total    $0.417  $0.450 

General  Expenses: 

Housing  and  heating $0.700  $0.757 

Superintendence,  power,  etc.  (10%)...   0.612  0.661 

Total    $1.312  $1.418 

Grand    totals $6-7335  $7.277 

The  roof  slabs  were  raised  from  the  casting  beds  by  means 
of  the  locomotive  crane  and  hooks,  as  shown  by  Fig.  245,  and 
loaded  onto  cars;  eight  slabs  made  a  carload.  The  cars  were 
run  to  the  work,  where  the  gin  poles  hoisted  the  slabs  one 
at  a  time  to  cars  running  on  a  track  built  on  timbers  laid  on 
top  of  the  roof  girders.  A  small  derrick  on  rafters  picked  the 
slabs  from  the  hand  car  and  set  them  in  place.  A  gang  bf 
15  men  erected  from  18  to  20  slabs  per  lo-hour  day.  With 
average  wages  at  21  cts.  per  hour  the  cost  of  erection  was 
(15  X  $2.10)  -T-  19  =  $1.66  per  slab,  or  $1.79  per  cu.  yd.  The 
total  cost  of  slabs  in  place  was  thus : 


SEPARATELY    MOLDED    PIECE    BUILDINGS.  523 

Item.  Per  slab.  Per  cu.  yd. 

Molding   $6.73  $7.27 

Erecting    1.66  1.79 


Total  $8.39  $9.06 

In  studying  these  cost  figures  their  limitations  must  be  kept 
in  mind.  Because  of  the  character  of  the  available  data  quan- 
tities had  in  several  cases  to  be  estimated  from  the  working 
drawings.  The  cost  of  lumber  for  and  of  framing  column  and 
girder  forms  is  not  included,  but  this  is  partly  balanced  at 
least  by  the  assumption  that  each  form  was  erected  complete 
for  each  column  and  girder,  which  was  not  the  case,  as  has 
been  stated.  Cost  of  plant  is  not  included  nor  is  cost  of  shor- 
ing the  columns  until  girders  and  struts  were  placed,  nor  are 
several  minor  miscellaneous  items. 

HOLLOW    BLOCK   WALL    CONSTRUCTION.— Three 

general  processes  of  molding  hollow  wall  blocks  of  concrete 
are  employed:  (i)  A  dry  mixture  is  heavily  tamped  into  a 
mold  and  the  block  is  immediately  released  and  set  aside  for 
curing;  (2)  a  liquid  is  poured  into  molds,  where  the  block  re- 
mains until  hard  :  (3)  a  medium  wet  mixture  is  compressed  into 
a  mold  by  hydraulic  presses  or  other  means  of  securing  great 
pressure.  The  molds  used  may  be  simple  wooden  boxes  with 
removable  sides  or  mechanical  molds  of  comparative  complex- 
ity. Generally  mechanical  molds,  or  concrete  block  machines 
as  they  are  commonly  called,  will  be  used.  There  are  a  score 
or  more  kinds  of  block  machines  all  differing  in  construction 
and  mode  of  operation.  None  of  them  will  be  described  here, 
but  those  interested  may  consult  "Concrete  Block  Manufac- 
ture" by  H.  H.  Rice  or  "Manufacture  of  Concrete  Blocks  and 
Their  Use  in  Building  Construction"  by  H.  H.  Rice,  Wm.  M. 
Torrance  and  others. 

Factory  Buildings,  Grand  Rapids,  Mich. — The  buildings 
ranged  from  one  to  four  stories  high  and  altogether  occupied 
some  74,000  sq.  ft.  of  ground.  The  owners  installed  a  block 
making  plant  fully  equipped  with  curing  racks,  two  Ideal  ma- 
chines, two  National  concrete  mixers,  5  h.p.  gasoline  engine, 
platens,  tools  and  a  Chase  industrial  railway. 


5^4 


CONCRETE    CONSTRUCTION. 


The  walls  were  constructed  of  24-in.  square  pilasters  of 
blocks  arranged  as  shown  by  Fig.  246,  connected  by  curtain 
wall  belt  courses  of  single  blocks.  The  blocks  were  8  x  8  x  16 
ins.,  and  after  molding  the  faces  were  bush  hammered  and  the 
edges  tooled.  The  pilasters,  consisting  of  four  blocks  laid 
around  an  8  x  8-in.  hollow  space,  were  solidified  by  pouring  the 
8  x  8-in.  space  and  all  but  the  three  outside  block  cavities  with 
wet  concrete.  The  interior  of  the  building  was  of  regulation 
mill  construction,  and  as  the  pilasters  reached  the  heights  for 
beam  supports  cast  iron  plates  with  downward  flanges  were 
set  in  the  concrete.  These  plates  had  a  cast  pin  projecting 
upward  to  fasten  the  beam  end. 


DO 

D 
D 

1 

D 

oo 

D 

Fig.  246.— Concrete  Block  Pilaster  for  a  Factory  Building. 

The  materials  used  for  the  block  were  Sandusky  Portland 
cement  and  J^-in.  bank  gravel  well  balanced  from  fine  to 
course.  The  blocks  were  molded  with  1-3  mortar  faces,  the 
mortar  being  water-proofed  by  a  mixture  of  Medusa  water- 
proofing compound.  All  concrete  was  machine  mixed.  The 
men  operating  the  block  machines  were  paid  i  ct.  for  each 
block  molded,  so  that  their  pay  depended  upon  the  energy 
with  which  they  worked.  The  men  handling  materials  and  en- 
gaged in  handling  and  curing  the  blocks  were  paid  $1.75  per 
day.  The  gravel  was  shoveled  from  the  railway  cars  onto  the 
screens  and  from  the  screen  piles  to  the  mixers.  The  gang  was 
organized  as  follows: 


SEPARATELY    MOLDED    PIECE    BUILDINGS.  525 

Item.  Per  day. 

8  men  handling  materials,  at  $1.75 $14.00 

5  men  operating  molds,  at  i  ct.  per  block 15.00 

1  man  mixing  facing  mortar,  at  $1.75 1.75 

2  men  loading  blocks  onto  trucks,  at  $1.75 3.50 

2  men  unloading  blocks  from  trucks,  at  $1.75 3.50 

3  men  sprinkling  blocks,  at  $1.75 5.25 

Total,  21  men  molding  and  curing  blocks $43«oo 

The  average  daily  run  was  1,500  blocks,  or  300  blocks  per 
machine. 

This  output  was  easily  maintained  after  the  gang  got  broken 
in;  sometimes  it  ran  higher  and  sometimes  lower,  but  the 
average  was  as  given.  The  men  operating  the  block  machines 
thus  earned  $3  each  per  day.  The  labor  cost  of  molding  and 
curing  per  block  was  thus  2.87  cts.  As  the  blocks  had  about 
25  per  cent,  hollow  space,  each  block  8  x  8  x  16  ins.  contained 
0.45  cu.  ft.  of  concrete;  a  cubic  yard  of  concrete,  therefore, 
made  60  blocks,  so  that  the  labor  cost  of  making  the  blocks 
was  60  X2.87  cts.  =  $1.72  per  cubic  yard.  This  cost  does  not 
include  foreman's  time,  materials,  interest,  depreciation  or 
general  expenses.  It  was  estimated  by  the  owners  that  the 
blocks  cost  them  9  cts.  apiece  cured,  or  about  $5.40  per  cubic 
yard  of  concrete.  This  9  cts.  evidently  includes  materials 
and  labor  alone. 

Upon  removal  from  the  molds  the  blocks  were  loaded  onto 
cars,  taken  to  a  large  shed  and  there  unloaded  onto  shelving 
arranged  to  hold  five  rows  of  blocks  one  above  the  other,  two 
blocks  opposite  each  other  on  each  shelf.  The  blocks  were  left 
in  the  shed  24  to  48  hours  to  get  the  preliminary  set,  then  they 
were  loaded  on  small  cars  and  taken  to  the  yard,  where  they 
were  removed  from  the  cars  and  stacked.  They  were  sprinkled 
every  day  for  six  days,  being  kept  covered  meanwhile  with 
oiled  cotton  cloth.  The  labor  costs  given  above  include  mold- 
ing, sprinkling  and  handling  the  blocks  up  to  this  point. 

To  lay  the  blocks  they  were  again  loaded  on  cars  and  run 
to  an  elevator  in  a  wooden  tower  outside  the  building.  The 
elevator  lifted  the  car  to  the  floor  on  which  the  blocks  were  to 
be  used,  where  it  was  run  off  onto  a  track  reaching  the  full 


526  CONCRETE    CONSTRUCTION. 

length  of  the  building.  The  blocks  were  unloaded  directly 
behind  the  masons.  Where  the  walls  were  high  enough  for 
scaffolding  the  blocks  were  unloaded  directly  onto  the  first 
scaffold  and,  when  necessary,  handed  up  to  the  scaffolds 
above.  The  masons  employed  were  regular  stone  masons  re- 
ceiving the  regular  scale  of  wages  of  $3.50  per  day.  The  num- 
ber of  blocks  laid  by  each  mason  was  125  per  day  in  building 
pilasters  and  200  per  day  in  building  plain  wall.  Sometimes 
250  blocks  per  day  per  man  were  laid  in  plain  wall  work.  The 
cost  per  block  of  laying  above  was  thus  2.8  cts.  pilasters  and 
1.75  cts.  in  plain  wall.  This  cost  does  not  include  transporting 
the  blocks  from  yard  or  of  handling  them  to  the  scaffold  be- 
hind the  masons,  nor  does  it  include  the  cost  of  materials  and 
labor  for  mixing  and  delivering  mortar. 

One  of  the  features  of  this  work  was  the  method  of  trans- 
porting the  blocks  by  cars.  A  complete  system  of  tracks  was 
provided  covering  the  block  plant  and  yard,  the  building  sites 
and  the  several  floors  of  the  buildings  themselves.  All  blocks 
and  other  materials  were  transported  by  cars  running  on  these 
tracks,  both  cars  and  tracks  being  of  the  type  made  by  the 
Chase  Foundry  &  Manufacturing  Co.  of  Columbus,  Ohio. 

Residence,  Quogue,  N.  Y. — The  following  record  of  meth- 
ods and  cost  of  constructing  a  concrete  block  residence  is 
furnished  by  Mr.  Noyes  F.  Palmer :  A  mixture  of  sand  and 
pebbles  was  had  on  the  site ;  screening  was  necessary  merely 
to  sort  out  the  odd  size  stones.  A  mixture  of  I  cement  and  5 
sand  was  really  a  1-2-3  mixture,  the  2  being  the  finest  grades  of 
sand  and  the  3  being  various  gravel  sizes — none  too  large, 
none  too  small — so  that  the  proportion  was  2/5  fine  sand  and 
3/5  gravel. 

The  concrete  was  hand  mixed,  and  as  the  gravel  had  always 
just  been  excavated  it  contained  moisture  and  did  not  have 
to  be  wetted.  The  sand  and  gravel  were  mixed  and  turned 
three  or  four  times  and  spread  out  thin,  and  the  cement  was 
carefully  spread  over  them  in  a  uniform  layer.  The  mass  was 
then  turned  three  or  four  times  until  the  eye  could  detect  no 
difference  in  color;  that  is,  each  grain  large  enough  for  the 
eye  to  discern  seemed  to  be  coated  with  cement.  After  this 
dry  mixing,  water  was  added  in  a  fine  spray — not  a  deluge 


SEPARATELY    MOLDED    PIECE    BUILDINGS. 


527 


from  a  pail — but  only  enough  to  moisten  the  mixture.  The 
mass  was  then  turned  three  or  four  times.  The  mixture  was 
then  shoveled  into  the  mold,  no  special  face  mixture  being 
used,  so  as  to  about  half  fill  it,  and  was  then  tamped  by  two 
men,  one  standing  on  each  side  of  the  machine.  Altogether 
three  layers  of  material  were  so  placed  and  tamped  and  then 
a  shovelful  of  sand  and  cement  mixture  was  spread  over  the 
top  to  permit  an  even  "strike-off." 

As  each  block  was  molded  it  was  carried  on  the  working 
plate  and  set  down  on  skids  properly  spaced  to  fit  the  marks 
on  the  plate.  This  is  an  important  detail  and  Mr.  Palmer  com- 
ments on  it  as  follows :  "The  writer  saw  inexperienced  men 
careless  about  it  and  who  would  break  the  backs  of  many 
blocks  by  not  having  the  skids  properly  placed.  After  the 
blocks  have  been  at  rest  for  half  an  hour  commence  to  spray 
them  with  a  revolving  garden  sprinkler  or  by  carefully  wetting 
with  a  sprinkling  pot  on  the  center  of  the  block  only.  The 
blocks  should  not  be  allowed  to  dry  out  for  at  least  ten  days 
after  removal  from  the  working  plate.  The  removal  from  the 
working  plate  can  be  done  the  morning  after  molding  and 
should  never  be  done  before  even  if  the  block  was  made  in 
the  morning.  In  removing  the  green  block  from  the  skids 
let  there  be  cones  of  sand  between  the  rows  of  blocks  and 
up-end  each  working  plate  so  as  to  let  the  end  of  the  block 
come  upon  the  sand  cushion.  Don't  twist  and  turn  the  block, 
and  to  remove  the  working  plate  pass  a  stick  through  the  core 
holes  in  both  block  and  plate  so  that  the  plate  will  not  fall 
when  loosened.  A  slight  rap  on  the  center  of  the  plate  will 
loosen  it.  As  soon  as  the  blocks  are  up-ended  commence  the 
spraying  and  soak  the  sand  underneath  the  block.  It  may 
seem  unnecessary  to  dwell  on  these  points  so  long,  but  barrels 
of  cement  and  barrels  of  money  have  been  wasted  by  neglect- 
ing to  supply  the  hardening  block  with  water.  Curing  is  just 
as  important  as  molding  in  making  concrete  blocks." 

The  block  construction  had  been  detailed  by  the  architect 
from  cellar  to  roof,  so  that  it  was  known  beforehand  how 
many  blocks  of  given  size  were  to  be  made.  The  unit  of 
length  was  32  ins.;  this  afforded  fractional  parts  of  8  ins., 
16  ins.  and  24  ins.,  therefore  all  openings  were  in  multiples  of 
8  ins.  Odd  sizes  were  made,  by  inserting  "blanks"  in  the  mold 


528  CONCRETE    CONSTRUCTION. 

box,  to  inches  or  fractions  of  an  inch  if  desired.  This 
unit  length  was  less  mortar  joints,  while  the  unit  of  height 
was  9  ins.,  or  the  same  as  four  ordinary  bricks  with  joints. 
The  floor  levels  were  calculated  in  multiples  of  9  ins.,  so  that 
the  wall  could  be  finished  all  around  where  the  beams  were  to 
be  seated.  This  beam  course  was  made  of  solid  blocks ;  that 
is,  no  cores  Were  used  in  molding  them.  With  the  machine 
used  no  change  was  required  to  mold  these  solid  blocks  except 
to  remove  the  cores.  The  core  holes  in  the  working  plate 
were  simply  covered  with  pieces  of  tin.  The  shape  of  the 
block  was  the  same  and  the  same  materials  were  used. 

The  best  record  in  making  blocks  for  this  work  was  30 
blocks,  8  x  9  x  32  ins.,  in  one  hour,  working  six  men,  three  mix- 
ing and  three  on  the  machine,  and  using  one  barrel  of  cement 
for  16  blocks.  This  was  a  record  run,  however,  a  fair  average 
being  20  blocks  per  hour,  or  200  per  ten  hours,  which  was  the 
day  worked.  We  have  then  the  cost  of  making  blocks  as 
follows : 

I  foreman,  at  $2.50 $  2.50 

5  helpers,  at  $2 10.00 

13  barrels  cement,  at  $2 26.00 

10  cu.  yds.  sand  and  gravel,  at  $i 10.00 

Interest  and  depreciation  on  machine 2.00 

Total  for  200  blocks $50.50 

This  gives  a  cost  per  block  of  $50.50  -^-  200  =  25*4  cts.  The 
displacement  in  the  wall  of  each  block  is  1.75  cu.  ft.,  or  the 
same  as  30  bricks. 

The  cost  of  laying  blocks  is  the  most  uncertain  item  in  the 
whole  industry.  Mr.  Palmer  states  that  he  has  known  of 
instances  where  it  cost  only  5  cts.  per  block  and  of  other 
instances  where,  because  of  the  difficulty  of  getting  help  and 
its  inexperience,  it  cost  15  cts.  per  block.  In  this  particular 
building  one  mason  and  three  helpers  laid  100  blocks  per  day. 
The  building  had  no  long  walls,  but  it  did  have  many  turns. 
The  cost  of  laying,  then,  was  as  follows : 


SEPARATELY    MOLDED    PIECE    BUILDINGS. 


529 


L  mason,   at   $4 $  4.00 

3  helpers,  at  $2 6.00 

Total  for  100  blocks $10.00 

This  gives  a  cost  for  laying  of  10  cts.  per  block.  We  have, 
then: 

Making  2,000  blocks   $505 

Laying  2,000  blocks 200 

Total   $705 

This  gives  a  cost  of  35/4  cts.  per  block  for  making  and 
laying. 

The  use  of  a  derrick  for  laying  the  blocks  proved  a  consid- 
erable item  of  economy  in  this  work.  This  derrick  cost  $50 
and  two  men  could  mount  and  move  it  on  the  floor  beams.  It 
had  a  boom  reaching  out  over  the  wall  and  was  operated  by  a 
windlass.  A  plug  and  feather  to  fit  the  center  6-in.  hole  in 
the  block  was  used  for  hoisting  the  blocks.  By  this  means 
blocks  only  seven  days  old  were  laid  without  trouble.  It  may 
be  noted  that  the  walls  were  kept  drenched  with  water  to  make 
sure  that  the  blocks  did  not  dry  out  until  they  were  at  least  28 
days  old.  In  laying  the  blocks  a  thin  lath  was  used  to  keep 
the  mortar  back  about  one  inch  from  the  face.  This  precau- 
tion will  prevent  much  labor  in  cleaning  the  walls  from  mortar 
slobber. 

Two-Story  Building,  Albuquerque,  N.  M.— The  following 
record  of  cost  of  making  9x10x32-^.  hollow  blocks  in  a 
Palmer  machine  and  of  laying  2,000  of  them  in  two-story 
building  walls  is  given  by  Mr.  J.  M.  Ackerman.  Sand  cost 
60  cts.  per  cu.  yd.,  and  cement  cost  $3  per  barrel.  Lime  cost 
30  cts.  per  bushel.  One  barrel  of  cement  made  20  blocks, 
using  a  1-4  sand  mixture.  In  making  2,000  blocks  about  100 
blocks,  or  5  per  cent.,  were  lost  by  blocks  breaking  in  hauling 
from  yard  to  building  or  by  cutting  blocks  to  fit  the  work. 
The  blocks  were  molded  by  piece  work  for  5  cts  per  block,  all 
materials,  tools  and  plant  being  supplied  to  the  molders. 
Three  men  with  one  machine  made  from  100  to  150  blocks  per 
day.  The  cost  was  as  follows: 


530  CONCRETE    CONSTRUCTION. 

Item.  Per  block. 

Cement,  at  $3  per  bbl $0.15 

Molding,  at  5  cts.  per  block 0.05 

Sand,  at  60  cts.  per  cu.  yd 0.03 

Carting,  yard  to  building 0.02 

Lime  and  sand  for  mortar 0.03 

Laying  in  wall   ' o.io 

Loss  in  making  and  cutting o.oi 

Total , $0.39 

As  each  block  gave  9X32  =  288  sq.  ins.,  or  2  sq.  ft.,  of 
wall  surface,  the  cost  of  the  wall  per  square  foot  was  19.5  cts. 
Assuming  40  per  cent,  hollow  space,  each  block  contained  I 
cu.  ft.  of  concrete,  which  cost  23  cts.,  or  $6.21  per  cu.  yd.,  for 
materials  and  molding.  Blocks  in  the  wall  cost  $10.55  Per  cu- 
yd.  of  concrete. 

General  Cost  Data. — The  following  data  are  given  by  Prof. 
Spencer  B.  Newberry.    The  average  weights  of  three  sizes  of 
hollow  blocks  are  as  follows : 
•Size,  ins.  P.  C.  Hollow  Space.     Weight,  Ibs. 

8x9x32  33  1-3  120 

10x9x32  331-3  150 

12  x  9  x  32  33  1-3  180 

Costs  of  materials  are  assumed  as  follows : 

Item.  Per  100  Ibs. 

Cement,  at  $1.50  per  bbl $0.40 

Hydrated  lime,  at  $5  per  ton $0.25 

Sand,  gravel  or  screenings,  at  25  cts.  per  ton $0.012 

Mixed  in  batches  of  750  Ibs.,  sufficient  for  six  8-in.  or  four 
12-in.  blocks,  the  cost  of  materials  per  batch  and  per  block 
will  be  for  a  1-4  mixture  as  follows: 

Item.  Per  Batch.     8-in.  Block.     12-in/ Block. 

150  Ibs.  cement $0.60  $0.10  $0.15 

600  Ibs.  sand  •      0.072  0.012  0.018 


Total $0.672  $0.112  $0.168 

In  general  a  factory  producing  600  8-in.  blocks  per  day  will 
require  25  men  to  operate  it.  At  an  average  wage  of  $i.8o  per 
day  the  following  is  considered  as  a  fair  estimate  of  cost : 


SEPARATELY    MOLDED    PIECE    BUILDINGS.  531 

Item.                                                     Per  Day.  Per  Block. 

Materials  for  600  blocks . . , .  . .  .     $  60  $0.10 

25  men,  at  $1.80 45  O-O?5 

Repairs   10  0.017 

Office  and  miscellaneous   20  0.034 


Total  $135  $0.226 

This  gives  for  8  x  9  x  32-in.  blocks  a  cost  of  about  $6.78  per 

cu.  yd.  of  concrete  for  materials  and  molding  or  of  11.3  cts.  per 

sq.  ft.  of  face. 

Mr.  L.  L.  Bingham  gives  the  following  as  the  average  cost 

per  square  foot  of  face  for  lo-in.  wall  from  data  collected  from 

a  large  number  of  block  manufacturers  operating  in  Iowa  in 

1905: 

Cement  at  $i  .60  per  bbl. 4.5  cts. 

Sand 2.0  cts. 

Labor  at  $i..83  per  day   3.8  cts. 


Total  cost  per  square  foot 10.3  cts. 

Assuming  one-third  hollow  space,  the  cost  for  materials 
and  molding  was  $5.05  per  cu.  yd.  of  concrete  not  including 
interest,  depreciation,  repairs,  superintendence  or  general  ex- 
penses. 


CHAPTER  XXI. 

METHODS  AND  COST  OF  AQUEDUCT  AND  SEWER 
CONSTRUCTION. 

Aqueducts  and  sewers  in  concrete  are  of  three  kinds:  (i) 
Continuous  monolithic  conduits :  (2)  conduits  laid  up  with 
molded  concrete  blocks,  and  (3)  conduits  made  up  of  sec- 
tions of  molded  pipe.  Block  conduits  and  conduits  of  molded 
pipe  are  rare  in  America  compared  with  monolithic  construc- 
tion ;  examples  of  each  are,  however,  given  in  succeeding  sec- 
tions, where  forms,  methods  of  molding,  etc.,  are  described. 
The  following  discussion  refers  to  monolithic  construction 
alone. 

FORMS  AND  CENTERS.-— Forms  and  centers  for  conduit 
work  have  to  meet  several  requirements.  They  have  to  be 
rigid  enough  not  only  to  withstand  the  actual  loads  coming  on 
them,  but  to  keep  from  being  warped  by  the  alternate  wetting 
and  drying  to  which  they  are  subjected.  They  have  also  to  be 
constructed  to  give  a  smooth  surface  to  the  conduit.  To  be 
economical,  they  have  to  be  capable  of  being  taken  down, 
moved  ahead  and  re-erected  quickly  and  easily.  The  carpenter 
costs  run  high  in  constructing  conduit  forms,  so  that  each 
form  has  to  be  made  the  most  of  by  repeated  use. 

Three  different  constructions  of  traveling  forms  are  de- 
scribed in  the  succeeding  sections.  For  small  work,  such 
forms  appear  to  offer  certain  advantages,  but  for  conduits  of 
considerable  size  their-  convenience  and  economy  are  uncer- 
tain. The  experience  with  the  large  traveling  form  employed 
on  the  Salt  River  irrigation  works  in  Arizona  was,  when  all 
is  said,  rather  discouraging.  The  authors  believe  that  for 
work  of  any  size  where  the  concrete  must  be  supported  for 
24  hours  or  more,  forms  of  sectional  construction  will  prove 
cheaper  and  more  expeditious  than  any  traveling  form  so  far 
devised. 

532 


AQUEDUCTS    AND    SEWERS. 


533 


No  class  of  concrete  work,  perhaps,  offer  so  good  an  op- 
portunity for  the  use  of  metal  forms  as  does  conduit  work.  The 
smooth  surface  left  by  metal  forms  is  particularly  advantage- 
ous, and  there  is  a  material  reduction  in  weight  and  a  large 
increase  in  durability  due,  both  to  the  lack  of  wear  and  to 
freedom  from  warping.  Steel  forms  of  the  Blaw  type  shown 
by  Fig.  247,  have  been  used  for  conduits  up  to  25  ft.  in  diam- 
eter. The  form  illustrated,  Fig.  247,  was  for  a  i2-ft.  3-in. 
sewer;  in  this  case  a  roof  form  alone  was  used,  but  full  cir- 


Fig.  247.— Blaw  Collapsible  Steel  Centering  for  Conduit  Construction, 
cular  and  egg-shape  forms  are  made.     The  Blaw  collapsible 
Steel  Centering  Co.,  of  Pittsburg,  Pa.,  make  and  lease  steel 
forms  of  this  type. 

Sectional  wooden  forms  for  conduits  of  large  diameters 
are  shown  by  the  drawings  in  several  of  the  succeeding  sec- 
tions. Figures  248  and  249  show  such  forms  for  small  diam- 
eters. The  form  shown  by  Fig.  248  is  novel  in  the  respect  that 
after  being  assembled  a  square  timber  was  passed  through 
it  lengthwise,  occupying  the  holes  B  and  having  its  ends  pro- 


534 


CONCRETE    CONSTRUCTION. 


jecting  and  rounded  to  form  gudgeons.  The  form  was  mounted 
with  these  gudgeons  resting  on  horses,  so  that  it  could  be 
rotated  and  thus  wound  with  a  narrow  strip  of  thin  steel 
plate.  Thus  sheathed,  the  form  was  lowered  into  the  trench 
and  the  concrete  was  placed  around  it.  When  the  arch  had 


Fig.   248.— Sectional  Steel  Wrapped  Wooden  Form  for  Conduit  Construction. 


been  turned,  the  wedges  A  were  driven  in  until  the  ribs  C 
dropped  into  the  slots  a  and  clear  of  the  steel  shell;  the  arch 
form  was  then  pulled  out  and  finally  the  invert  form,  leaving 
the  steel  shell  in  place  to  hold  the  concrete  until  hard.  The 
strip  of  steel  was  then  removed  by  pulling  on  one  end  until  it 


Fig.  249.— Invert  Form  for  Conduit  Construction. 

unwound  like  cord  from  the  inside  of  a  ball  of  twine.  Steel 
strips  6  ins.  wide  and  1-24  in.  thick  were  used  successfully  in 
constructing  a  5~ft.  egg-shaped  sewer  in  Washington,  D.  C. 
The  forms  were  made  in  sections  16  ft.  long,  and  were  taken 
out  as  soon  as  the  concrete  had  been  placed. 


AQUEDUCTS    AND    SEWERS."  535 

The  form  shown  by  Fig.  249,  is  an  invert  form,  used  in 
constructing  the  sewer  shown  by  Fig.  249,  built  at  Medford, 
Mass.,  in  1902,  by  day  labor.  The  concrete  was  1-3-6  gravel. 
The  forms  for  the  invert  were  made  collapsible  and  in  lo-ft. 
lengths.  The  two  halves  were  held  together  by  iron  clamps 
and  hook  rods.  The  morning  following  the  placing  of  the  con- 
crete the  hook  rods  were  removed  and  turnbuckle  hooks  were 
put  in  their  places,  so  that  by  tightening  the  turnbuckle  the 
forms  were  carefully  separated  from  the  concrete.  The  con- 
crete was  then  allowed  to  stand  24  hours,  when  the  arch  cen- 
ters were  set  in  place.  These  centers  were  made  of  %  x  il/2- 
in.  lagging  on  2-in.  plank  ribs  2  ft.  apart,  and  stringers  on  each 
side.  Wooden  wedges  on  the  forward  end  of  each  section 
supported  the  rear  end  of  the  adjoining  section.  The  forward 
end  of  each  section  was  supported  by  a  screw  jack  placed  un- 
der a  rib  2  ft.  from  the  front  end.  To  remove  the  centers,  the 
rear  end  of  a  small  truck  was  pushed  under  the  section  about 
18  ins.;  an  adjustable  roller  was  fastened  by  a  thumb  screw 
to  the  forward  rib  of  the  center;  the  screw  jack  was  lowered 
allowing  the  roller  to  drop  on  a  run  board  on  top  of  the  truck ; 
the  truck  was  then  pulled  back  by  a  tail  rope  until  the  adjust- 
able roller  ran  off  the  end  of  the  truck ;  whereupon  the  truck 
was  pulled  forward  drawing  the  center  off  the  supporting 
wedges  of  the  rear  section.  Each  lineal  foot  of  sewer  re- 
quired i*4  cu.  yds.  of  excavation  which  cost  74.2  cts.  per  foot, 
and  I  cu.  ft.  of  brick  arch  which  cost  $12.07  Per  cu-  yd-,  or  44-2 
cts.  per  lineal  foot  of  sewer.  The  invert  required  4  cu.  ft.  of 
concrete  per  foot,  which  cost  as  follows : 

Item.  Per  cu.  yd. 

Portland  cement:  at  $2.15  per  bbl $2.292 

Labor  mixing  and  placing   3-OI7 

Cost    of    forms    0.187 

Labor   screening   gravel    0.471 

Carting    °-592 

Miscellaneous   .      , 0.146 


Total  -  •  .$6.705 

The  cost  of  the  invert  was  thus  $1.002  per  lin.  ft.  of  sewer. 


536 


CONCRETE    CONSTRUCTION. 


Collapsible  metal  forms  for  manholes  and  catchbasins  are 
made  by  several  firms  which  make  block  and  pipe  molds.  A 
cylindrical  wooden  form  construction  is  shown  by  Fig-.  250. 
The  outside  form  consists  of  three  segments  of  a  cylinder  made 
of  2-in.  lagging  bolted  to  hoops.  Bent  lugs  on  the  ends  of 
the  hoops,  were  provided  with  open  top  slots  and  were  bolted 
together  through  I  x  %-in.  bars  which  extended  the  full  length 
of  the  form  between  lugs.  The  assembled  form  was  collapsed 
by  pulling  up  on  the  bars,  thus  lifting  the  bolts  out  of  the  slots. 


Ourside    Cylinder  wside   Cylinder 

Fig.   250. — Form  for  Circular   Catch   Basin   or   Manhole. 

The  inner  mold  is  also  made  in  three  sections  with  strap 
hinges  at  two  of  the  joints  and  at  the  third  joint  a  wedge- 
shaped  stave.  The  other  details  are  shown  by  the  drawing. 
To  mold  the  top  of  the  basin  two  cone-shaped  forms  are  used, 
an  outer  form  made  in  one  piece  and  an  inner  form  made  in 
sections.  Some  26  catch  basins  were  built  in  Keney  Park, 
Hartford,  Conn.,  by  Mr.  H.  G.  Clark,  at  a  cost  of  $7  apiece 
for  concrete  in  place,  and  thefe  was  closely  I  cu.  yd.  of  con- 
crete in  each. 


AQUEDUCTS    AND    SEWERS. 


537 


CONCRETING.— Except  for  pipes  of  small  diameter,  the 
concreting  is  done  in  sections,  each  section  being  a  day's 
work.  Continuity  of  construction  has  not  proved  successful, 
except  for  pipes  of  moderate  size,  in  the  few  cases  where  it 
has  been  tried.  Examples  of  continuous  construction  meth- 
ods are  given  in  succeeding  sections.  Methods  of  molding 
and  laying  cast  concrete  pipe  are  also  best  shown  by  the 
specific  examples  given  further  on.  In  concreting  large  diam- 


n 


n 


Fig.  251.— Cross-Section  of  Pinto  Creek  Irrigation  Conduit. 

e.ters,  the  work  may  be  done  by  molding  successive  full  barrel 
sections,  or  by  molding  first  the  invert  and  then  the  roof  arch, 
each  in  sections.  The  engineer's  specifications  generally  stipu- 
late which  plan  is  to  be  followed.  Construction  joints  between 
sections  are  molded  by  bulkhead  forms  framed  to  produce  the 
type  of  joint  designed  by  the  engineer;  the  most  common 
type  is  the  tongue  and  groove  joint. 


538 


CONCRETE    CONSTRUCTION. 


For  small  diameters  built  with  traveling  forms,  a  compara- 
tively dry  concrete  is  essential,  but  when  the  centers  are  left 
in  place  until  the  concrete  has  set,  a  wet  mixture  is  preferable, 
as  it  is  more  easily  placed  and  worked  around  the  reinforce- 
ment in  the  thin  shells.  Mixers  are  commonly  specified  even 
for  small  work,  because  of  their  generally  more  uniform  and 
homogeneous  product.  Portable  mixers  hauled  along  the  bank 
and  discharging  into  the  forms  through  chutes,  furnish  a 
cheap  and  rapid  arrangement  where  the  section  being  built 


"Upper  Stationary — 
Plates 


Moving:  Mould 
CAlligator) 


Lower  Stationary 
Plates 


Fig.  252.— Traveling  Form  for  Pinto  Creek  Conduit. 

has  a  considerable  yardage.  The  examples  given  in  succeed- 
ing sections  present  various  methods  of  mixing  and  placing 
concrete  in  conduit  work. 

REINFORCED  CONDUIT,  SALT  RIVER  IRRIGA- 
TION WORKS,  ARIZONA.— The  pipe  had  the  cross-sec- 
tion shown  by  Fig.  251,  and  formed  a  syphon  carrying  water 
under  the  bed  of  a  creek.  The  concrete  was  a  1-2^-4  fine 
gravel  mixture,  mixed  by  hand  on  boards  150  ft.  apart  along 
the  'line.  The  shell  was  reinforced  as  shown. 


AQUEDUCTS    AND    SEWERS  539 

The  forms  consisted  of  an  outside  form  constructed  as 
shown  by  Fig.  251,  by  inserting  2l/2-m.  x  5^2  ft.  lagging  strips 
in  the  metal  ribs.  The  inside  form  was  designed  to  permit 
continuous  work  by  moving  the  form  ahead  as  the  concreting 
progressed.  It  consisted  as  shown  by  Fig.  252,  of  an  invert 
form  on  which  an  arch  form  was  carried  on  rollers.  The 
invert  form  was  pulled  along  by  cable  from  a  horse-power 
whim  set  ahead,  being  steered,  aligned  and  kept  to  grade  by 
being  slid  on  a  light  wooden  track.  It  had  the  form  of  a  long 
half  cylinder,  with  its  forward  end  beveled  off  to  form  a  scoop- 
like  snout.  The  arch  center  consisted  of  semi-circular  rings  2 
ft.  long,  set  one  at  a  time  as  the  work  required.  Each  ring, 
when  set,  was  flange-bolted  to  the  one  behind,  and  each  was 
hinged  at  three  points  on  the  circumference  to  make  it  col- 
lapsible. In  operation,  the  invert  form  was  intended  to  be 
pulled  ahead  and  the  arch  rings  to  be  placed  one  after  another 
in  practically  a  continuous  process.  So  that  the  arch  rings 
might  continue  supported  after  the  invert  form  was  drawn  out 
from  under  them*  invert  plates  similar  to  the  arch  plates  were 
inserted  one  after  another  in  place  of  the  shell  of  the  invert 
form.  The  plan  provided  very  nicely  for  continuous  work, 
but  continuous  work  was  found  impracticable  for  all  but  about 
2,500  ft.  of  the  6,000  ft.  of  conduit  built.  The  reason  for  this 
seems  to  have  been  at  least  in  a  great  measure,  the  slow  set- 
ting cement  made  at  the  cement  works  established  by  the 
Government,  at  Roosevelt.  In  building  the  first  300  ft.  of 
conduit,  a  commercial  cement  was  used  and  a  progress  of 
1 20  lin.  ft.  of  pipe  per  24  hours  was  easily  made.  This  work 
was  done  in  June.  Later,  but  still  in  warm  weather,  using 
the  Government  cement  and  70  ft.  of  arch  plates,  not  more 
than  70  ft.  of  pipe  could  be  completed  in  24  hours;  if  the 
plates  were  taken  down  sooner,  patches  of  concrete  fell  out 
or  peeled  off  with  them.  As  the  weather  grew  colder,  this 
difficulty  increased,  until  finally,  the  idea  of  continuous  work 
was  abandoned  and  for  some  3,500  ft.  of  conduit  only  one  8- 
hour  shift  per  day  was  worked.  In  December  and  January 
the  plates  had  to  remain  in  place  three  days,  so  that  the 
progress  was  only  24  ft.  per  day ;  in  warm  weather  this  rate 
was  increased  to  40  ft.  per  day. 


540 


CONCRETE    CONSTRUCTION. 


Costs  were  kept  on  two  sections  of  one  of  the  lines  and  the 
figures  shown  in  the  accompanying  table  were  obtained. 

A  gang  consisted  of  a  foreman  at  $175  per  month,  a  sub- 
foreman  at  $3.50  per  day,  and  the  following  laborers  at  $2.50 
per  day :  one  bending  the  reinforcement  rings ;  two  placing 
the  reinforcement ;  four  taking  down,  moving  and  erecting  the 
stationary  plates;  four  placing  the  concrete  and  outside  lag- 
ging; two  wheeling  concrete;  six  mixing  concrete;  one  wheel- 
ing sand  and  gravel;  one  watering  the  finished  pipe;  four 
laying  track  for  the  steering  apparatus,  moving  the  super- 
structure and  hangers,  mixing  boards,  runways,  etc. ;  one 
pointing  and  finishing  inside  the  pipe;  and  one  on  the  whim 
and  doing  miscellaneous  work.  The  labor  was  principally 
Mexican,  and  only  fairly  efficient. 

It  is  important  to  note  that  the  costs  given  in  the  table 
are  labor  costs  only  of  mixing  and  placing  concrete  and  mov- 


Wages 
Per 
Day. 
f  Laying"  track  for  steer- 
|       ing  alligator   $  5.00 

May,  '06. 
714 
Lin.  Ft. 
Cost. 

$  71.48 

July,  '06. 
1,009 
Lin.  Ft. 
Cost. 

$  43  98 

Cost 
Per 
Lin.  Ft. 

$0.0670 

Per 

Cu.  Yd. 

$0.16 

4  men  -j  Moving      and       erect- 
ing superstructure....     5.00 
4  men    Moving  plates             .         10  00 

299.94 
202  50 

358.44 
253  44 

0.3821 
0  2646 

0.93 
0  65 

58  50 

2  50 

0  0354 

0  08 

1  man    Bending  rings                        2  50 

32  87 

59  87 

0  0538 

0  13 

2  men    Placing  reinforcement..     5.00 
12  men    Mixing  and  placing  con- 
crete                               .     30  00 

126.94 
709  68 

138.13 
949  74 

0.1538 
0  9631 

0.38 
2  34 

1  man    Watering  finished  pipe.     2.50 
1  man    Painting     and       brush- 
coating  inside       .  .   .  .     2.50 

45.00 
96.50 

78.27 
117  37 

0.0716 
0  1241 

0.17 
0  31 

Blacksmith's  work 

30  00 

25  00 

0  0319 

0  08 

1  man    Whim          ...     2  50 

23  87 

28  75 

0  0306 

0.07 

1  man    Screening  and     hauling 
ing  sand  and  gravel..     2.50 

183.13 

300.00 

0.2804 

0.68 

Total   . 

$1,880.41 

$2,355.49 

$2.4584 

$5.98 

ing   forms ;    they   do   not    include    engineering,    first    cost    of 
forms,   concrete   materials,   reinforcement   or   grading. 

CONDUITS,  TORRESDALE  FILTERS,  PHILADEL- 
PHIA, PA. — At  the  Torresdale  plant  of  Philadelphia  filtration" 
system  the  clear  water  conduits  are  reinforced  concrete.  The 
following  description  is  composed  from  information  furnished 
the  authors  in  1904  by  the  Bureau  of  Filtration,  Mr.  John  W. 
Hill,  then  chief  engineer.  The  lengths  of  the  several  con- 


AQUEDUCTS    AND    SEWERS. 


541 


duits  are  as  follows:  576  ft.  of  7^-ft.,  782  ft.  of  8-ft.,  1,050  ft. 
of  9-ft.,  and  1,430  ft.  of  lo-ft.  horseshoe  conduit.  All  sizes  of 
conduit  have  the  same  cross-sectional  form — the  cross-section 
of  the  9-ft  conduit  is  shown  by  Fig.  253,  and  all  are  rein- 
forced by  expanded  metal  arranged  as  indicated.  The  con- 
crete is  a  1-3-5,  24-in.  stone  mixture.  The  conduits  were  first 
designed  with  circular  sections,  but  before  construction  had 
been  begun  on  these  plans,  experience  had  been  obtained  in 
building  a  circular  sewer  that  made  a  change  to  the  horseshoe 
section  appear  desirable.  In  the  circular  sewer  work,  great 


Concrete. 


Fig.  253.— Section  of  9-ft.   Conduit,  Philadelphia  Filter  Plant. 

difficulty  had  been  found  in   properly  placing  and  ramming 
the  concrete  in  the  lower  quarters  of  the  circular  section. 

Forms. — The  forms  used  for  the  several  sizes  of  conduit 
were  all  of  the  same  general  type,  but  improvements  in  detail 
were  made  as  successive  sizes  were  built.  The  last  form  to  be 
designed  was  that  for  the  9~ft.  section  and  this  was  the  best 
one;  it  is  shown  by.  Fig.  254.  The  forms  were  built  in  sec- 
tions from  12  ft.  to  i$y2  ft.  long.  They  were  covered  with  Nc. 
27  galvanized  sheet  iron,  and  this  covering  was  found  of  ad- 
vantage both  in  giving  a  smooth  finish  and  in  prolonging  the 


542 


CONCRETE    CONSTRUCTION. 


life  of  the  centers.  The  important  feature  is  the  construction 
in  sections  which  could  be  set  up  and  broken  down  by  simply 
inserting  and  removing  the  connecting  bolts.  Three  sets  of 
forms  were  made  for  each  size  of  conduit. 

Procedure  of  Work. — The  first  operation  in  building  a  sec- 
tion of  conduit  was  to  set  to  exact  line  and  grade  and  the 
length  of  the  form  in  advance  of  the  finished  work  the  bulk- 
head shown  by  Fig.  255.  In  this  space  the  invert  concrete  was 
deposited  and  formed  to  a  plane  i  in.  below  the  finished  invert 
bottom.  The  two  bottom  sections  of  the  form  were  then  as- 
sembled and  located  by  bolting  one  end  to  the  last  preceding 


Lagging, 
Covered  with 

.Shezt  Iroh. 


,    „ 

L/  OL     //)  ««_V 

c7  /  */  ^ 

Fig.   254.— Form  for  9-ft.   Conduit  Philadelphia   Filter  Plant. 

form  and  inserting  the  other  end  into  the  bulkhead.  About 
two  tons  of  pig  iron  were  then  placed  on  the  invert  form  to 
keep  it  from  floating  while  the  liquid  granolithic  mixture  was 
being  poured  into  the  i-in.  space  between  the  form  and  the 
invert  concrete.  In  building  up  the  sides  a  facing  form  was 
used  for  placing  the*  granolithic  finish.  This  consisted  of 
"boards"  of  sheet  steel  ribbed  transversely  on  one  side  with 
^4 -in.  pipe  and  on  the  other  side  with  il/2-m.  pipe.  Two  boards 
were  used  on  each  haunch,  slightly  lapping  in  the  center,  as 
follows :  The  board  was  placed  with  the  small  ribs  against 


AQUEDUCTS    AND    SEWERS. 


543 


the  form  and  the  larger  ribs  kept  the  expanded  metal  just  3 
ins.  from  the  face  of  the  form.  A  6-in.  depth  of  concrete  was 
placed  between  the  metal  board  and  the  outside  form  or 
planks,  then  6  ins.  of  granolithic  was  poured  into  the  i-in. 
space  between  the  center  and  the  board  and  finally  the  board 
was  raised  6  ins.  and  the  concrete  and  granolithic  mixture 
tamped  together.  With  the  board  in  its  new  position,  another 
layer  of  concrete  and  granolithic  was  placed.  Toward  the 
crown  the  granolithic  mixture  was  made  stiff  and  simply 
plastered  onto  the  mold.  The  expanded  metal  was  cut  into 
sheets  corresponding  to  the  length  of  the  sides  of  the  form  and 
lapped  6  ins.  in  all  directions ;  the  bulkhead  having  a  slot  as 

,,/fey 


Fig.  255.— Bulkhead  Form  for  Conduits,  Philadelphia  Filter  Plant. 

shown  to  permit  the  metal  to  project  6  ins.  from  the  face  of 
the  concrete  in  order  to  tie  two  sections  together  and  also 
having  a  rib  which  formed  a  mortise  in  the  face  of  the  shell 
of  concrete  to  key  it  to  the  succeeding  section. 

All  the  conduits  were  built  in  sections  from  12  ft.  to  13^ 
ft.  long,  and  there  was  very  little,  if  any,  difference  in  the 
labor  required  to  build  a  section,  in  from  eight  to  ten  hours, 
of  any  of  the  three  sizes.  One  foreman  and  18  men  on  the 
top  of  the  trench  mixed  and  handled  the  concrete  and  grano- 
lithic mortar  while  one  foreman,  one  carpenter  and  seven  men 
in  the  trench  set  the  forms  and  placed  and  rammed  the  con- 
crete for  one  section  in  generally  eight  hours.  About  one-third 


544  CONCRETE    CONSTRUCTION. 

of  the  concrete  for  the  whole  work  was  mixed  in  a  portable 
cubical  mixer  of  y2  cu.  yd.  capacity,  and  the  remainder  was 
mixed  by  hand.  Owing  to  the  relatively  small  amount  of  con- 
crete used  per  day,  about  20  cu.  yds.,  it  was  found  that  there 
was  practically  no  difference  in  the  cost  of  machine  mixing 
and  of  hand  mixing.  The  9-ft.  conduit  as  an  average  of  the 
three  sizes,  contained  20  cu.  yds.  of  concrete,  1,200  sq.  ft.  of 
expanded  and  required  125  bags  of  cement  for  a  section  13^ 
ft.  long.  The  cost  of  the  work  excluding  excavation  and 
profit,  but  including  forms,  metal,  concrete  materials  and 
labor,  was  about  $10.50  per  cu.  yd. 

CONDUIT,  JERSEY  CITY  WATER  SUPPLY.— In  con- 
structing the  8y2-ft.  reinforced  concrete  conduit  for  the  Jersey 
City  water  supply,  use  was  made  of  forms  without  bottoms. 
Each  form  was  made  of  segmental  sections  12^/2  ft.  long  of 
wood  covered  with  sheet  steel.  They  were  set  end  to  end  in 
the  trench,  resting  on  6-in.  concrete  cubes  which  were  finally 
permanently  embedded  in  the  invert  concrete.  In  each  form 
there  was  a  scuttle  about  2  ft.  square  at  the  crown,  and  the 
bottom  was  open  between  the  curves  of  the  invert  haunches. 
The  form  being  set  and  greased  and  the  reinforcement  placed, 
the  concrete  was  deposited  on  the  outside  and  forced  by  means 
of  tamping  bars  down  the  curve  of  the  invert  haunches  until 
it  filled  the -whole  space  between  the  form  and  the  earth  and 
appeared  at  the  edges  of  the  bottom  opening  in  the  form. 
Concrete  was  then  thrown  through  the  scuttle  and  the  invert 
screeded  into  shape.  The  concreting  of  the  sides  and  crown 
of  the  arch  was  then  completed,  using  outside  forms  except  for 
about  5  ft.  of  the  crown,  the  scuttle,  of  course,  being  closed  by 
a  fitted  cover.  The  centers  were  left  in  place  about  48  hours. 
The  concrete  was  a  i  cement  7  sand  and  run  of  the  crusher 
2-in.  broken  stone  mixture,  and  was  made  so  wet  that  it  would 
flow  down  an  incline  of  I  on  8.  The  mixing  was  done  in  por- 
table Ransome  mixers,  set  on  the  trench  bank  alongside  the 
work  and  discharging  by  chute  into  dished  shoveling  boxes 
provided  with  legs  to  set  on  the  erected  forms.  Coal  scoops 
were  used  in  shoveling  from  the  box  into  the  forms  and  were 
found  superior  to  shovels  in  keeping  the  relative  proportions 
of  water  and  solids  constant. 


AQUEDUCTS    AND    SEWERS. 


545 


TWIN  TUBE  WATER  CONDUIT  AT  NEWARK,  N.  J. 

— In  constructing  the  Cedar  Grove  Reservoir,  at  Newark,  N. 
J.,  two  conduits  side  .by  side  were  built  across  the  bottom 
from  gate  house  to  tunnel  outlet.  A  section  of  one  of  the  con- 
duits showing  the  form  construction  and  the  arrangement  of 
the  reinforcement  is  given  by  Fig.  256.  The  concrete  was  a 
1-2-5  I  ^2 -in.  stone  mixture  and  the  reinforcement  was  No.  10  3- 
in.  mesh  expanded  metal.  The  method  and  cost  of  construction 
are  given  as  follows,  by  Mr.  G.  C.  Woollard,  the  engineer  for 
the  contractors.  ^  * 


Fig.  256.— Conduit  for  Cedar  Grove  Reservoir,  Newark,  N.  J. 

"The  particular  thing  that  was  insisted  upon  by  both  Mr. 
M.  R.  Sherrerd,  the  chief  engineer  of  the  Newark  Water 
Department  and  Mr.  Carlton  E.  Davis,  the  resident  engineer 
at  Cedar  Grove  Reservoir,  in  connection  with  these  conduits, 
was  that  they  be  built  without  sections  in  their  circumference, 
that  the  whole  of  the  circumference  of  any  one  section  of  the 
length  should  be  constructed  at  one  time.  They  were  per- 
fectly willing  to  allow  us  to  build  the  conduit  in  any  length 
section  we  desired,  so  long  as  we  left  an  expansion  joint  oc- 
casionally which  did  not  leak. 


546  CONCRETE    CONSTRUCTION. 

"The  good  construction  of  these  conduits  was  demonstrated 
later,  when  the. section  stood  40  Ibs.  pressure  to  the  square 
inch,  and,  in  addition,  I  may  say  that  these  conduits  have 
not  leaked  at  all  since  their  construction.  This  shows  the 
wisdom  of  building  the  conduit  all  round  in  one  piece,  that  is, 
in  placing  the  concrete  over  the  centers  all  at  one  time,  in- 
stead of  building  a  portion  of  it,  and  then  completing  that 
portion  later,  after  the  lower  portion  had  had  an  opportunity 
to  set. 

"The  centers  which  I  designed  on  this'  work  were  very 
simple  and  inexpensive,  as  will  be  gathered  from  the  cost  of 
the  work,  when  I  state  that  this  conduit,  which  measured  only 
0.8  cu.  yd.  of  concrete  to  the  lineal  foot  of  single  conduit,  cost 
only  $6.14  per  cu.  yd.,  built  with  Atlas  cement,  including  all 
labor  and  forms  and  material,  and  expanded  metal.  The 
forms  were  built  in  16  ft.  lengths,  each  16  ft.  length  having 
five  of  the  segmental  ribbed  centers  such  as  are  shown  in  Fig. 
256,  viz.,  one  center  at  each  end  and  three  intermediate  cen- 
ters in  the  length  of  16  ft.  These  segments  were  made  by  a 
mill  in  Newark  and  cost  90  cts.  apiece,  not  including  the  bolts. 
We  placed  the  lagging  on  these  forms  at  the  reservoir,  and 
it  was  made  of  ordinary  2x4  material,  surfaced  on  both  sides, 
with  the  edges  bev.eled  to  .the  radius  of  the  circle.  These 
pieces  of  2x4  were  nailed  with  two  lod.  nails  to  each  seg- 
ment. The  segments  were  held  together  by  four  l/2-in.  bolts, 
\vhich  passed  through  the  center,  and  1 1/2 -in.  wooden  tie  block. 
There  was  no  bottom  segment  to  the  circle.  This  was  left 
open,  and  the  whole  form  held  apart  by  a  piece,  B,  of  3  x  2. 
spruce,  with  a  bolt  at  each  end  bolted  to  the  lower  segment 
on  each  side. 

"The  outside  forms  consisted  of  four  steel  angles  to  each 
16  ft.  of  the  conduit,  one  on  each  end,  and  two,  back  to  back, 
in  the  middle  of  each  16  ft.  length.  These  angles  were  2x3, 
with  the  2-in.  side  on  the  conduit,  and  the  3-in.  side  of  the 
angle  had  small  lugs  bolted  on  it  at  intervals,  to  receive  the 
2x12  plank,  which  was  slipped  down  on  the  outside  of  the 
conduit,  as  it  was  raised  in  height.  The  angles  were  held  from 
kicking  out  at  the  bottom  by  stakes  driven  into  the  ground, 
and  held  together  at  the  top  by  a  ^-in.  tie-rod, 


AQUEDUCTS    AND    SEWERS.  547 

"The  conduit  was  8  ins.  thick,  save  at  the  bottom,  where 
it  was  12  ins.  The  reason  for  the  12  ins.  at  the  bottom  was 
that  the  forms  had  to  have  a  firm  foundation  to  rest  on,  in 
order  to  put  all  the  weight  required  by  the  conduit  on  them 
in  one  day  or  at  one  time,  without  settling.  We  therefore 
excavated  the  conduit  to  grade  the  entire  length,  and  de- 
posited a  4-in.  layer  of  concrete  to  level  and  grade  over  the 
entire  length  of  the  conduit  line.  This  gave  us  a  good,  firm 
foundation,  true  and  accurate  to  work  from,  and  this  is  the 
secret  of  the  good  work  which  was  done  on  these  conduits. 
If  you  examine  them,  you  will  say  that  they  are  one  of  the 
neatest  jobs  of  concrete  in  this  line  that  has  been  built,  espe- 
cially with  regard  to  the  inside,  which  is  true,  level  and  abso- 
lutely smooth.  [The  authors  can  confirm  this  statement.] 
When  the  conduit  is  filled  with  water,  it  falls  off  with  abso- 
lutely no  point  where  water  stands  in  the  conduit,  owing  to 
its  being  out  or  the  proper  amount  of  concrete  not  being  de- 
posited. 

"The  centers  were  placed  in  their  entirety  on  a  new  length 
of  conduit  to  be  built,  resting  upon  four  piles  of  brick,  two 
at  each  end  as  shown.  The  first  concrete  was  placed  in  the 
forms  at  the  point  marked  X  and  the  next  concrete  was 
dropped  in  through  a  trap  door  cut  in  the  roof  of  the  con- 
duit form  at  the  point  marked  F.  This  material  was  dropped 
in  to  form  the  invert,  and  this  portion  was  shaped  by  hand 
with  trowels  and  screeded  to  the  exact  radius  of  the  conduit. 
The  concrete  was  then  placed  continuously  up  the  sides,  and 
boards  were  dropped  in  the  angles  which  I  have  mentioned, 
and  which  served  as  outside  form  holders  till  the  limit  was 
reached  at  the  top,  where  it  was  impossible  to  get  the  concrete 
in  under  the  planking  and  thoroughly  tamped.  At  this  point 
the  top  was  formed  by  hand  and  with  screeds. 

"Each  i6-ft.  length  of  this  conduit  was  made  with  oppo- 
site ends  male  and  female  respectively,  that  is,  we  had  a  small 
form  which  allowed  the  concrete  to  step  down  at  one  end  to  3 
ins.  in  thickness  for  8  ins.  back  from  the  end  of  the  section, 
and  on  the  other  end  of  the  section  it  allowed  it  to  step  down 
to  3  ins.  in  thickness  in  exactly  the  opposite  way,  making  a 
scarf  joint.  This  was  not  done  at  every  16  ft.  length,  unless 
only  16  ft.  were  placed  in  one  day.  We  usually  placed  48  ft. 


548  CONCRETE    CONSTRUCTION. 

a  day  at  one  end  of  the  conduit  with  one  gang  of  men.  This 
was  allowed  to  set  24  hours,  and,  whatever  length  of  conduit 
was  undertaken  in  a  day,  was  absolutely  completed,  rain  or 
shine,  and  the  gang  next  day  resumed  operations  at  the  other 
end  of  the  conduit  on  another  48  ft.  length.  This  was  com- 
pleted, no  matter  what  the  weather  conditions  were,  and, 
towards  the  close  of  this  day  the  forms  placed  on  the  preced- 
ing day  were  being  drawn  and  moved  ahead. 

"The  method  used  in  moving  these  forms  ahead  for  another 
day's  work  is  probably  one  of  the  secrets  of  the  low  cost  of  this 
work,  and  it  is  one  which  we  have  never  seen  employed  be- 
fore. The  bolt  at  A,  Fig.  256,  was  taken  out,  and  the  tie  brace 
B  thrown  up.  We  had  hooks  at  the  points  C.  A  turnbuckle 
was  thrown  in,  catching  these  hooks,  and  given  several  sharp 
turns,  causing  the  entire  form  to  spring  downward  and  in- 
wards, which  gave  it  just  enough  clearance  to  be  carried  for- 
ward, without  doing  any  more  striking  of  forms  than  pulling 
the  bolt  at  A.  This  method  of  pulling  the  forms  worked  ab- 
solutely satisfactorily,  and  never  gave  any  trouble,  and  we 
were  able  to  move  the  forms  very  late  in  the  day  and  get  them 
all  set  for  next  day's  work,  giving  all  the  concrete  practically 
24  hours'  set,  as  we  always  started  concreting  in  the  morning 
at  the  furthest  end  of  the  form  set  up  and  at  the  greatest 
distance  from  the  old  concrete  possible  in  the  48  ft.  length, 
as  the  furthest  form  had,  of  course,  to  be  moved  first,  it  being 
impossible  to  pass  one  form  through  the  other. 

"Six  i6-ft.  sections  of  these  forms  were  built,  and  three  were 
used  each  day  on  each  end,  as  shown  by  the  diagram  MN, 
Fig.  256,  which  gives  the  day  for  the  month  for  the  comple- 
tion of  each  of  seven  48-ft.  sections. 

"A  gang  of  men  simply  shifted  on  alternate  days  from  end 
to  end  of  the  conduit,  although  several  sections  were  in  prog- 
ress at  one  time ;  and  of  course,  finally,  when  a  junction  was 
made  between  any  division,  say  of  1,000  ft.  to  another  1,000 
ft.,  one  small  form  was  left  in  at  this  junction  inside  of  the 
conduit,  and  had  to  be  taken  down  and  taken  out  the  entire 
length  of  the  conduit. 

"The  centers  for  a  i6-ft.  length  of  this  conduit  cost  com- 
plete for  labor  and  material,  $18.30,  but  they  were  used  over 
and  over  again;  and,  after  this  conduit  was  completed,  they 


AQUEDUCTS    AND    SEWERS. 


549 


were  taken  away  for  use  at  other  points,  so  that  the  cost  is 
hardly  appreciable,  and  the  only  charge  to  centers  that  we 
made  after  the  first  cost  of  building  the  centers,  was  on  ac- 
count of  moving  them  daily.  Part  of  this  conduit  was  built 
double  (two  6-ft.  conduits)  and  part  single,  the  only  difference 
being  that,  where  the  double  conduit  was  built,  two  forms 
were  placed  side  by  side,  and  not  so  much  was  undertaken  in 
one. day. 

"These  conduits,  when  completed  and  dried  out,  rung  exact- 
ly like  a  6o-in.  cast-iron  pipe,,  when  any  one  walked  through 
them  or  stamped  on  the  bottom." 

Mr.  Woollard  gives  the  following  analysis  of  the  cost  per 
cubic  yard  of  the  concrete-steel  conduit  above  described : 

Per  cu.  yd. 

1.3  bbl.   cement    $143 

10  cu.  ft.  sand 0.35 

25  cu.  ft.  stone  i.io 

26  sq.  ft.  expanded  metal,  at  3  cts 0.78 

Loading  and  hauling  materials  2,000  ft.   to  the   mixing 

board  (team  at  $4.50)   0.50 

Labor  mixing,  placing,  and  ramming 1.38 

Labor  moving  forms    0.60 


Total   $6.14 

Wages  were  17^  cts.  per  hr.  for  laborers  and  50  cts.  per 
hr.  for  foremen.  The  concrete  was  1-2-5,  a  barrel  being  as- 
sumed to  be  3.8  cu.  ft.  The  concrete  was  mixed  by  hand 
on  platforms  alongside  the  conduit.  The  cost  of  placing  and 
ramming  was  high,  on  account  of  the  expanded  metal,  the 
small  space  in  which  to  tamp,  and  to  the  screeding  cost.  When 
forms  were  moved  they  were  scraped  and  brushed  with  soft 
soap  before  being  used  again. 

From  Mr.  Morris  R.  Sherrerd,  Engineer  and  Superintendent, 
Department  of  Water,  Newark,  N.  J.,  we  have  received  the  fol- 
lowing data  which  differ  slightly  from  those  given  by  Mr. 
Woollard.  The  differences  may  be  explained  by  the  fact  that 
the  cost  records  were  made  at  different  times.  Mr.  Sherrerd 
states  (Sept.  26,  1904,)  that  each  batch  contains  4  cu.  ft.  of 
cement,  8  cu.  ft.  of  sand,  and  20  cu.  ft.  of  stone,  making  22 
cu.  ft.  of  concrete  in  place.  One  bag  of  cement  is  assumed  to 


550  CONCRETE    CONSTRUCTION. 

hold  i  cu.  ft.  He  adds  that  a  lo-hour  day's  work  ior  a  gang 
is  63  lin.  ft.  of  single  6-ft.  conduit  containing  47.4  cu.  yds. 
of  concrete  and  1,260  sq.  ft.  of  expanded  metal.  This  is 
equivalent  to  ^  cu-  yd.  of  concrete  per  lin.  ft.  The  total  cost 
of  material  for  one  complete  set  of  forms  64  ft.  long  was  $160; 
and  there  were  7  of  these  sets  required  to  keep  two  gangs  of 
men  busy,  each  gang  building  63  lin.  ft.  of  conduit  a  day. 
Since  the  total  length  of  the  conduit  was  3,850  ft.,  the  first 
cost  of  the  material  in  the  forms  was  18  cts.  per  lin.  ft. 

Cost  of  Labor  on  6-ft.  Conduit : 

Per  day.  Per  cu.  yd. 

i  foreman  on  concrete  $  3.35  $0.07 

1  water  boy  0.75  o.oi 

ii  men  mixing  at  $1.75  .  . I9-25  0.39 

5  men  mixing  at  $1.50 7.50  0.16 

4  men  loading  stone  at  $1.40 5.60  0.12 

4  men  wheeling  stone  at  $1.40 ,  5.60  0.12 

2  men  loading  sand  at  $1.40 2.80  0.06 

2  men  wheeling  sand  at  $1.40 2.80  0.06 

1  man  placing  concrete  at  $1.75 1.75  0.04 

6  men  placing  concrete  at  $1.50 9.00  0.19 

2  men  supplying  water  at  $1.50 3.00  0.06 

i  man  placing  expanded  metal  at  $2. 2.00  0.04 

1  man  placing  expanded  metal  at. $1.50...      1.50  0.03 

Total  labor  on  concrete   $64.90  $!-35 

Cost  of  Labor  Moving  Forms : 

Per  day. Per  cu.  yd. 
4  carpenters  placing  forms   $13.00  $0.27 

2  helpers  placing  forms 4.00  0.08 

i  carpenter  putting  up  boards  for  outside 

forms 2.75  0.06 

1  helper    putting    up    boards    for    outside 

forms    -  2.25  0.05 

2  helpers  putting  up  boards    for    outside 

forms    3.50  0.07 

i  team  hauling  timber 4.50  0.09 

i  helper  hauling  lumber 1.75  0.04 

Total  labor  moving  forms $3r-75  $0.66 


AQUEDUCTS    AND    SEWERS. 


551 


It  will  be  noted  that  it  required  two  men  to  bend  and  place 
the  700  Ibs.,  or  1,260  sq.  ft.,  of  expanded  metal  required  for 
63  lin.  ft.  of  conduit  per  day,  which  is  equivalent  to  l/2c  per  lb., 
or  3  cts.  per  sq.  ft.,  for  the  labor  of  shaping,  placing  and 
fastening  the  metal. 

CIRCULAR    SEWER,    SOUTH    BEND,    INDIANA.— 

In  building  2,464  ft.  of  66-in.  circular  reinforced  concrete  sewer 
at  South  Bend,  Ind.,  in  1906,  the  method  of  construction  il- 
lustrated in  Figs.  257,  258  and  259  was  employed.  The  sewer 
has  a  9-in.  shell  buttressed  on  the  sides  and  is  reinforced  every 
12  ins.  by  a  3-i6xi-in.  peripheral  bar  in  the  sides  and  roof 
and  3  ins.  in  from  the  soffit.  Each  bar  is  composed  of  three 
pieces,  two  side  pieces  from  15  ins.  below  to  6  ins.  above 


?  Temp/ef 


Fig.   257.— Form   for  South   Bend   Sewer   (First   Stage). 

springing  lines  and  a  connecting  roof  bar  attached  to  the  side 
bars  by  cotter  pins.  Two  grades  of  concrete  were  used,  a  1-3-6 
bank  gravel  concrete  for  the  invert  and  a  1-2-4  bank  gravel 
concrete  for  the  arch.  The  invert  was  given  a  ^-in.  plaster 
coat  of  i -i  mortar  as  high  as  the  springing  lines. 

Forms  and  Concreting. — In  constructing  the  sewer  the 
trench  was  excavated  so  as  to  give  a  clearance  of  I  ft.  on  each 
side  and  was  sheeted  as  shown  by  Fig.  257.  The  sewer  was 
built  in  12  ft.  sections  as  follows:  The  bottom  of  the  trench 
was  shaped  as  nearly  as  possible  to  the  grade  and  shape  of 
the  base  of  the  sewer.  Four  braces  to  each  12  ft.  section  were 
then  nailed  across  the  trench  .between  the  lowest  rangers  on 
the  trench  sheeting.  A  partial  form  consisting  of  a  vertical 


552 


CONCRETE    CONSTRUCTION. 


row  of  lagging  was  set  on  each  of  the  outside  lines  of  the 
sewer  barrel  as  shown  by  Fig.  257.  Each  section  of  this  lag- 
ging was  held  by  stakes  driven  into  the  trench  bottom  and 
nailed  at  their  tops  to  the  cross  braces  as  shown  by  Fig.  258. 
A  template  for  the  invert  was  then  suspended  from  the  cross 
braces  by  pieces  nailed  to  the  four  ribs  of  the  template  and 


-Sheeflngr 


i -Side  Pieces  of  \ 

J  Reinforcement  Bandit. 


J 


Brace 


Fig.  258. — Form  for  South  Bend  Sewer  (Second  Stage), 
to  the  cross  braces  as  shown  by  Fig.  257.  The  concrete  was 
now  placed  and  carried  to  the  top  of  the  template,  which 
was  then  removed.  The  side  pieces  of  the  reinforcing  bars 
were  then  set  and  fastened  as  shown  by  Fig.  258.  The  side 
forms  extending  up  to  the  springing  lines  were  then  placed. 


Fig.  259.— Form  for  South  Bend  Sewer  (Third  Stage). 

They  were  held  in  position  by  braces  nailed  to  their  ribs  at  the 
tops  and  by  other  braces  fitting  into  notches  in  the  ends  of 
their  ribs  at  the  bottom.  The  concrete  was  then  carried  up 
to  the  springing  lines,  the  arch  centers  in  two  pieces  were 
placed ;  the  arch  bar  of  the  reinforcement  was  placed  and  the 


AQUEDUCTS    AND    SEWERS. 


553 


extrados  forms  erected  up  to  the  45°  lines,  all  as  shown  by  Fig. 
259.  The  placing  of  the  arch  concrete  completed  the  sewer 
barrel.  The  outside  forms  and  bracing  were  removed  about  24 
hours  after  the  completion  of  the  arch  and  back  filling  the 
trench  was  begun  immediately,  but  the  inside  forms  were  left 
in  place  for  two  weeks ;  they  were  then  removed  by  the  sim- 
ple process  of  knocking  out  the  notched  braces.  By  building 
several  lengths  of  invert  first  and  following  in  succession  by 
the  side  wall  construction  and  then  by  the  arch  construction, 
the  form  erection  and  the  concreting  proceeded  without  inter- 
ruption by  each  other.  It  was  also  found  that,  by  making 
bends  in  the  form  of  polygons  with  10  ft.  sides  instead  of  in 
the  form  of  curves,  there  was  a  material  saving  in  expensive 
form  work.  To  overcome  the  friction  of  the  angles  in  such 
bends  an  additional  fall  was  provided  at  these  places.  All  con- 
crete was  made  in  a  Smith  mixer  mounted  on  trucks  so  that 
it  could  be  moved  along  the  bank  of  the  trench  and  dis- 
charging into  a  trough  leading  to  the  work. 

Labor  Force  and  Cost. — With  a  gang  of  12  men  from  24  to 
36  ft.  of  sewer  was  built  per  lo-hour  day,  working  only  part 
of  the  time  on  actual  concreting.  The  disposition  of  the 
force  mixing  and  laying  concrete  and  the  wages  were  as  fol- 
lows: 

Item.  Per  day. 

Six  wheelers,  at  18.5  cts.  per  hour $11.10 

One  mixer,  at  22.5  cts.  per  hour 2.25 

One  dumper,  at  18.5  cts.  per  hour 1.85 

Four  placers,  at  22.5  cts.  per  hour 9.00 

Total $24.20 

There  were  0.594  cu.  yd.  of  concrete  per  lineal  foot  of  sewer 
and  its  cost  is  given  as  follows: 


554  CONCRETE    CONSTRUCTION. 

Item.  Per  cu.  yd. 

Cost  of  gravel   $0.774 

Cost  of  sand  0.36 

Cost  of  cement i  .50 

Cost  of  steel  reinforcement 0.84 

Cost  of  labor,  mixing  and  placing  concrete 1.094 

Cost  of  moving  forms,  templates,  etc °-757 

Cost  of  forms,  templates,  etc 0.589 

Cost  of  finishing,  plastering,  etc 0-639 

Cost  of  tools  and  general  expenses 0.841 


Total    $7.394 

SEWER  INVERT,  HAVERHILL,  MASS.— In  construct- 
ing sewers  with  concrete  inverts  at  Haverhill,  Mass.,  in  1905, 
use  was  made  of  the  traveling  form  or  mold  shown  by  Fig.  260. 
The  form  consists  of  an  inner  and  an  outer  shell,  the  annular 
space  between  which  forms  the  mold ;  in  operation  the  annular 
space  is  filled  with  concrete,  then  the  outer  shell  is  pulled 
ahead  from  underneath,  leaving  the  inner  shell  in  place.  A 
second  inner  shell  is  then  adjusted  to  the  outer  shell  in  its  new 
position,  the  annular  mold  is  concreted  and  the  outer  shell 
again  pulled  ahead.  Continued  repetition  of  the  operations 
described  completes  the  invert.  The  merit  of  the  device  lies 
in  the  fact  that  the  inner  shell  is  not  moved  until  the  concrete 
has  attained  some  degree  of  rigidity;  when,  in  such  devices,  the 
inner  mold  is  slid  ahead  en  the  green  concrete  it  is  likely  so 
to  "drag"  forward  the  material  that  a  rough  and  pitted  sur- 
face results. 

Mold  Construction. — Referring  to  the  drawings  of  Fig.  260, 
A  is  the  outer  mold  of  sheet  steel  bent  to  the  required  shape  of 
the  outer  surface  of  the  conduit  to  be  constructed.  A  rib,  or 
angle,  B,  is  riveted  to  the  inside  of  the  mold  at  its  front  end  and  a 
diaphragm  C  of  plank  is  securely  fastened  to  the  rear  side  of  the 
rib.  The  opposite  or  rear  end  of  the  mold  is  open.  Angles  D 
forming  tracks  are  riveted  inside  the  mold  a  short  distance  below 
the  edges  and  reaching  their  full  length.  The  inner  mold  com- 
prises a  steel  shell  E  curved  to  the  form  of  the  inside  of  the  con- 
duit; inside  this  steel  shell  is  a  reinforcing  lagging,  and  at  each 
end  there  is  a  wooden  diaphragm  F.  Passing  through  both  end 


AQUEDUCTS    AND    SEWERS. 


555 


diaphragms  and  having  its  ends  flush  with  the  end  planes  of  the 
mold  is  a  timber  G.  Rearward  projecting  lips  e  are  secured  to 
the  lagging  at  the  rear  end  of  the  mold  and  on  each  side  of  the 
timber  G.  The  diaphragms  F  have  each  two  arms  f  which  pro- 
ject horizontally  beyond  the  surface  of  the  inner  mold  and  engage 
the  tracks  D;  locking  dogs  H  are  pivoted  to  the  arms  /  so  as  to 
hook  under  the  track  angles  D  and  hold  the  inner  form  from 
rising.  Setting  on  the  inner  mold  is  an  inverted  V-shaped  de- 
flector /;  its  edges  are  flush  with  the  sides  of  the  mold  and  its 
purpose  is  to  facilitate  the  placing  of  the  concrete.  There  is  also 
a  movable  diaphragm  K,  fitting  loosely  inside  the  outer  mold  A 
and  bearing  against  the  end  of  the  inner  mold  E.  The  length 
of  the  inner  mold  E  is  about  one-half  that  of  the  outer  mold  A; 
as  a  rule  several  iriner  molds  are  provided  with  one  outer  mold. 


1 

TV 

5>>B 

1  f    i    F--' 

-|--A-j  — 

1:1.!  ._  • 

1  M 

S             ! 

| 

i 

i 

Bear   Elevation. 


Section  C-D. 


Section  E-F. 


Section  6-H. 
Fig.    260. — Traveling  Invert  Form   for  Sewer  Construction. 

Mode  of  Operation. — In  using  the  device  described  the  outer 
mold  A  is  first  placed  in  the  trench  with  its  rear  end  at  the 
end  of  the  trench.  An  inner  mold  E  is  then  suspended  on 
the  tracks  of  the  outer  mold  and  locked  therein  by  the  dogs 
H,  with  its  rear  end  flush  with  the  rear  end  of  the  outer  mold. 
The  partition  K  is  then  placed  in  position  -against  the  forward 
end  of  the  inner  mold  and  a  jack  /  of  any  suitable  form  is  in- 
terposed between  diaphragms  K  and  C,  the  jack  being  ex- 
tended sufficiently  to  press  diaphragm  K  firmly  against  the 
front  end  of  the  inner  mold.  The  deflector  7  is  next  placed 
in  position  on  the  inner  mold  and  the  concrete  is  forced  down 
with  an  iron  rammer  between  the  two  molds,  so  as  to  fill  com- 


556  CONCRETE    CONSTRUCTION. 

pletely  the  annular  space.  The  deflector  aids  in  directing  the 
concrete  into  this  space,  as  will  be  obvious.  After  the  mold 
has  been  filled  and  the  concrete  compacted  as  much  as  possi- 
ble, the  jack  is  operated  to  separate  the  diaphragms  K  and 
C,  and  as  the  partition  K  is  pressed  against  one  end  of  the 
mass  of  concrete  which  has  been  laid,  the  opposite  end  of 
which  abuts  against  the  end  of  the  trench,  it  follows  that  any 
backward  movement  of  the  diaphragm  K  will  compress  the 
concrete.  This  movement  will  be  practically  inappreciable  in 
distance,  but  enough  to  compact  thoroughly  the  concrete  and 
fill  any  voids.  The  action  of  the  jack  will  also  push  for- 
ward the  diaphragm  C  and  the  outer  mold  A,  the  latter  being 
withdrawn  from  beneath  the  inner  mold  and  the  newly  laid 
concrete,  the  tracks  D  of  the  outer  mold  being  drawn  from 
beneath  the  arms  /  of  the  inner  mold,  leaving  the  latter  be- 
hind resting  on  the  freshly  laid  concrete.  Further  compression 
of  the  concrete  after  it  has  been  left  by  the  outer  mold  will 
fill  the  spaces  between  the  inner  mold  and  the  surface  of  the 
trench.  The  outer  mold  is  moved  forward  in  this  manner  a 
distance  equal  to  the  length  of  the  inner  mold,  and  then  the 
diaphragm  K  is  drawn  forward  and  another  inner  mold  is 
lowered  into  the  outer  mold  exactly  as  was  the  first  one.  The 
jack  is  then  placed,  the  concrete  deposited  and  the  outer  mold 
again  advanced  exactly  as  before.  As  the  outer  mold  ad- 
vances, the  inner  molds  become  disengaged  one  after  another 
and  are  set  ahead;  in  practice,  enough  inner  molds  are  pro- 
vided to  enable  the  concrete  to  harden  sufficiently  to  keep 
its  position  when  it  becomes  necessary  to  take  up  successively 
the  rearmost  molds  and  place  them  ahead. 

Haverhill  Sewer  Work. — The  work  at  Haverhill,  Mass., 
previously  mentioned  in  which  the  form  just  described  was 
used,  was  a  24-in.  circular  sewer  with  6-in.  walls.  The  outer 
form  was  36  ins.  in  diameter  and  6  ft.  2  ins.  long;  the  inner 
form  was  24  ins.  in  diameter  and  3  ft.  long.  Angle  B  was 
3  ins.  and  the  track  angles  D  were  il/2  ins.;  diaphragm  K 
was  made  of  two  thicknesses  of  3-in.  plank  and  diaphragm  C 
of  one  thickness  of  3-in.  plank,  the  other  diaphragms  were  of 
2-in.  plank.  The  shells  of  the  molds  were  of  %-ni.  steel  plate ; 
the  jack  was  an  ordinary  screw  jack.  Eight  inner  molds  were 
used. 


AQUEDUCTS    AND    SEWERS.  557 

The  form  used  at  Haverhill  was  built  by  the  city  carpenter, 
the  metal  portions  being  made  in  a  boiler  shop.  Its  cost  was 
not  ascertained,  but  was,  it  is  thought,  about  $75.  The  con- 
crete used  was  a  1-3-5  stone  mixture,  with  cement  costing  $2 
per  barrel,  sand  $1.50  per  load  of  36  cu.  ft.,  and  stone  $2.50 
per  load  of  36  cu.  ft.  The  men  were  paid  25  cts.  per  hour. 
Records  kept  on  265  ft.  of  invert,  or,  theoretically,  19.3  cu. 
yds.  of  concrete,  gave  the  following  figures : 

Per  Per 

lin.  ft.      cu.  yd. 
Labor,  setting  and  moving  forms,  42  hours,  at 

25  cts $0.05        $0.67 

Labor,    mixing,    placing    and    wheeling    concrete, 

179  hours,  at  25  cts 0.16          2.19 


Total  labor  cost $0.21         $2.86 

With  the  ordinary  1-3-5  mixture  the  cost  of  materials  would 
run  about  as  follows: 

Per  cu.  yd. 

Cement,  0.96  bbl.,  at  $2 $i-92 

Sand,  0.47  cu.  yd.,  at  $1.13  O-53 

Stone,  0.78  cu.  yd.,  at  $1.88 i-47 

Total  cost  materials   $3-92 

Two  men  were  worked  in  the  trench,  one  alternately  ram- 
ming the  concrete  into  place  and  working  the  jack,  and  the 
other  shaping  the  trench  ahead  and  assisting  in  bringing  the 
rear  forms  ahead. 

The  form  described  was  invented  by  Mr.  Robert  R.  Evans, 
of  Haverhill,  Mass.,  and  has  been  patented  by  him. 

2Q-FT.  SEWER,  ST.  LOUIS,  MO.— The  following  account 
of  the  method  and  cost  of  constructing  162  ft.  of  very  large 
sewer  section  at  St.  Louis,  Mo.,  is  compiled  from  information 
furnished  by  Mr.  Curtis  Hill. 

The  cross-section  of  the  sewer  is  given  by  Fig.  261,  which 
also  shows  the  arrangement  of  the  reinforcing  bars.  Johnson 
corrugated  bars,  old  style,  are  used  for  reinforcement.  The 
sections  of  the  various  reinforcing  bars  are:  Longitudinal 
bars,  0.18  sq.  in.;  invert  bars,  0.7  sq.  in.,  and  arch  bars,  0.7 


558 


CONCRETE    CONSTRUCTION. 


sq.  in.  The  spacing  of  the  bars  and  the  arrangement  of  the 
splices  are  indicated  on  the  drawings  of  Fig.  261.  All  splices 
have  a  lap  of  36  ins.  Some  gravel  concrete  has  been  used  in 
the  invert,  but  most  of  the  concrete  has  been  crushed  lime- 
stone and  Mississippi  River  channel  sand.  The  proportions 
were  1-3-6  in  the  invert  and  1-2-5  in  the  arch.  The  arch  was 
computed  by  Prof.  Greene's  method.  The  ultimate  strength 
of  concrete  in  compression  was  taken  as  2,000  Ibs.  per  sq.  in. 
and  the  working  strength  at  500  Ibs.  per  sq.  in.  The  elastic 
limit  of  the  reinforcing  bars  was  taken  at  50,000  Ibs. 


* 


Fig.   261. — Harlem   Creek   Sewer,   St.   Louis,   Mo. 

The  trenching  was  done  by  wheel  scrapers  to  the  amount 
of  waste.  Then  a  cableway  was  erected  spanning  the  entire 
length  of  the  section  and  the  remainder  of  the  material  taken 
out.  The  last  4  or  5  ft.  in  depth  were  in  limestone  and  the 
excavated  rock  was  taken  by  cableway  to  dump  carts  which 
took  it  to  the  crusher  and  returned  with  crushed  rock  to  be 
used  for  concrete.  This  rock  foundation  was  taken  advantage 
of  to  reduce  the  amount  of  invert  concrete. 


AQUEDUCTS    AND    SEWERS. 


559 


In  constructing  the  sewer  proper  the  invert  was  first  con- 
creted to  template  to  the  height  shown  in  Fig.  262.  The  arch 
forms  were  then  placed  as  shown  in  Fig.  262,  and  the  roof  arch 
concreted.  Both  templates  and  arch  forms  were  constructed 
of  wood.  The  arch  forms  were  moved  ahead  on  iron  rails  and 
jacked  into  place.  The  ribs  were  2  x  lo-in.  pieces  and  were 
spaced  4  ft.  on  centers;  the  lagging  was  2-in.  tongue  and 
grooved  stuff  and  was  smeared  with  crude  oil.  The  reinforc- 


Fig.  262.— Center  for  Harlem  Creek  Sewer. 

ing  bars  shown  in  Fig.  261  were  bent  to  proper  radius  by 
means  of  a  wagon  tire  bender  and  were  held  in  place  by  tem- 
plates. The  concrete  was  all  mixed  by  two  Chicago  Improved 
Cube  mixers  operated  by  electric  power. 

The  cost  records  of  constructing  the  section  of  2Q-ft.  sewer 
so  far  built  are  not  susceptible  of  complete  analysis,  but  the 
following  figures  can  be  given.  The  prices  of  materials  were 
as  follows: 


560  CONCRETE    CONSTRUCTION. 

Cement,  per  barrel $1.80 

Sand,  per  cubic  yard 0.75 

Broken  stone,  per  cubic  yard i.oo 

Reinforcing  bars,  per  pound 0.02 

Vitrified  brick,  per  1,000   12.00 

The  wages  paid  different  classes  of  labor  were : 

Per  hour.  Per  hour. 

Firemen    $0.50          Helpers   $0.25 

Laborers     °-I75       Carpenters    0.55 

Laborers     0.20         Engineers 0.50 

Laborers     0.25         Timekeepers    0.25 

Laborers     0.28         Watchmen    ai75 

Laborers    0.3025     Hostlers    OtI75 

Bricklayers    0.66  2-3     Teams    0.60 

Taking  up  the  several  items  of  work  in  order,  the  excava- 
tion amounted  to  21,400  cu.  yds.,  of  which  1,400  cu.  yds.  were 
rock  excavation.  The  cost  of  excavation  was  as  follows : 

Total.  Per  cu.  yd. 

Earth,   excavation    $7,640  $0.38 

Earth  bracing 2,000  o.io 

Rock    excavation    1,400  i.oo 

Rock,  dynamite,  tools,  etc   560  0.40 

The  cost  of  crushing  the  excavated  rock  and  returning  it 
to  the  mixer  was  $i  per  cu.  yd. 

The  cost  of  the  concrete  work  was  as  follows : 

Per  cu.  yd. 

1.30  bbl.   cement  at  $1.80   $2.34 

.044  cu.  yd.  sand  at  75  cts 0.33 

i  cu.  yd.  broken  stone  at  $i    i.oo 

Total  concrete  materials   $8-67 

There  were  1,600  cu.  yds.  of  concrete  placed  at  a  cost  of  for: 

Total.       Per  cu.  yd. 

Mixing  and  placing    $1,180  $0.7375 

Forms        2,000  1.25 

Moving   forms    400  0.25 


Total  for  forms  and  labor $3,580  $2.2375 


AQUEDUCTS    AND    SEWERS.  561 

For  reinforcing  the  concrete  86,600  Ibs.  of  steel,  or  about 
55  Ibs.  per  cu.  yd.  were  used.  The  cost  of  placing  and  bend- 
ing this  steel  was  as  follows : 

Total.          Per  Ib. 

Cost  of  placing $172          0.1986  ct. 

Cost  of  bending  52          0.06      ct. 

We  can  now  summarize  the  cost  of  the  concrete  work 
proper  of  this  sewer  as  follows: 

Items.  Per  cu.  yd. 

Cement,    sand    and   stone    $3.67 

55  Ibs.  steel  at  2  cts i.io 

Forms,  labor  and  .materials   1.25 

Mixing  and   placing   concrete   labor 0.74 

Placing  steel  at  0.1986  ct.  per  Ib o.ii 

Bending  steel  at  0.06  ct.  per  Ib 0.03 

Moving  forms    0.25 

Total  labor  and  materials $7-I5 

To  get  the  total  cost  of  the  sewer  proper  we  must  add  the 
cost  of  the  vitrified  brick  invert  paving.  There  were  71  cu. 
yds.  of  this  paving  and  its  cost  was  as  follows: 

Per  cu.  yd. 

0.6  bbls.  cement  at  $1.80 $1.08 

0.25  cu.  yd.  sand  at  75  cts 0.19 

450  bricks  at  $12  per  M 54° 

Labor  laying,  71  cu.  yds.  at  $180.33 2-54 

Total    $9-21 

None  of  the  preceding  figures  includes  the  plant  charges. 
The  plant  cost  $12,000  and  the  cost  of  running  it  during  the 
work  described  was  $2,000.  In  explanation  it  should  be  noted 
that  the  plant  served  for  building  some  1,340  lin.  ft.  of  27~ft. 
sewer  as  well  as  for  the  section  described. 

SEWER  AT  MIDDLESBOROUGH,  KY.— In  construct- 
ing an  oval  sewer  4  ft.  high  at  Middlesborough,  Ky.,  two 
steel  forms  in  lo-ft.  sections  were  used.  As  shown  in  Fig.  263, 
T-iron  ribs  were  spaced  5  ft.  apart,  fastened  together  at  the 
top  by  longitudinal  angle  irons,  and  at  the  bottom  by  a  sheet 
of  steel  22  ins.  wide,  forming  the  bottom  of  the  invert.  The 


562 


CONCRETE    CONSTRUCTION. 


lagging  for  the  sides  consists  of  movable  5-ft.  lengths  of  chan- 
nel iron,  secured  by  sliding  bolts.  After  the  bottom  of  the 
trench  has  been  roughly  shaped  with  concrete,  a  lo-ft.  section 
of  invert  forms  is  lowered  and  suspended  by  the  cross-beams, 
and  the  space  beneath  packed  with  concrete ;  then  a  channel 
iron  is  slid  into  place  and  bolted,  and  concrete  packed  behind 
it,  and  so  on  until  the  invert  is  made.  The  next  lo-ft.  section 
is  then  built  while  the  first  is  hardening.  Upon  the  comple- 
tion of  the  second  section,  the  channel  iron  sides  of  the  first 
section  are  removed,  and  then  the  rib  framework  is  lifted 


Fig.  263.— Invert  Form  for  Sewer  Construction. 

out.  Wood  arch  centers  are  then  put  in  place  and  an  inch  of 
i  :  2  plaster  spread  over  the  lagging  before  placing  the  con- 
crete for  the  arch,  which  is  6  ins.  thick. 

The  cost  per  100  ft.  of  this  sewer  was  as  follows  (prices  be- 
ing assumed  for  cement  and  labor)  : 

Bottom  concrete.  Cost  per  100  ft. 

18.5  bbls.  cement,  at  $1.50 $  27.75 

2.7  cu.  yds.  sand,  at  $1.00 2.70 

15  cu.  yds.  stone,  at  $1.00 15.00 

17  days  labor,  at  $1.50 2S-S° 


AQUEDUCTS    AND    SEWERS. 


563 


Bottom  Mortar  Lining. 

25.25  bbls.   cement,   at  $1.50 37.85 

7.5  cu.  yds.  sand,  at  $1.00 7.50 

22  days  labor,  at  $1.50 33-OO 

Sewer  Arch. 

26  bbls.  cement,  at  $1.50   39.00 

3.9  cu.  yds.  sand,  at  $1.00 3.90 

13.6  cu.  yds.  stone,  at  $1.00 13.60 

21  days  labor,  at  $1.50 31-5° 

Cost  per  100  ft .$237.30 


I'Ptirtland  Cement  Mortar 


Fig.  264.— Sewer  at  Cleveland,  Ohio. 

INTERCEPTING  SEWERS,  CLEVELAND,  O.— An  in- 
tercepting sewer  some  3^  miles  long,  of  the  form  and  con- 
struction shown  in  Fig.  264,  was  built  at  Cleveland,  Ohio,  in 
1904.  The  construction  consists  of  a  plain  concrete  invert 
lined  with  two  courses  of  shale  bricks,  and  having  two  rows 
of  anchor  bars  set  in  the  side  walls  so  that  the  bars  of  one  row 
are  staggered  with  respect  to  those  of  the.  other  row.  The 
anchor  bars  are  2x^-in.  steel,  and  are  spaced  30  ins.  apart 


564  CONCRETE    CONSTRUCTION. 

in  each  row.  To  the  anchor  bars  are  bolted  arch  reinforc- 
ing bars  arranged  as  shown,  and  these  arch  bars  have  bolted 
to  them  eight  lines  of  il/2  x  %-in.  longitudinal  bars.  A  natural 
cement  concrete  is  used  for  the  invert  and  side  walls.  The 
arch  is  Portland  cement  concrete  of  normally  a  1-3-7^,  il/2- 
in.  screened  stone  mixture,  but  where  the  voids  in  the  broken 
stone  exceeded  40  per  cent.,  it  is  a  1-3-6  mixture.  The  invert 
bricks  are  laid  in  Portland  cement  mortar  and  the  arch  has 
a  mortar  lining  and  is  waterproofed  with  i-in.  of  mortar  on 
top. 

Forms. — Separate  forms  were  used  for  the  invert  and  for 
the  arch  ring.  Regarding  these,  the  engineer,  Mr.  Walter  G. 
Parmley,  remarks: 

One  of  the  first  forms  used  in  the  sewer  was  like  a  piece  of 
segmental  arch  centering  inverted,  and  with  the  lagging 
nailed  fast  to  the  ribs.  The  trouble  with  this  form  is  that  it 
is  difficult  to  tamp  concrete  under  the  bottom  portion  of  the 
form,  and  hence  a  very  rough  surface  is  produced.  Much 
better  results  were  obtained  by  omitting  the  lagging  boards 
on  the  bottom  and  at  the  sides  till  a  point  was  reached  where 
the  inclination  of  the  concrete  surface  was  about  45°.  The 
concrete  for  the  bottom  could  then  be  worked  down  between 
the  ribs,  thorough  tamping  done,  and  a  good  surface  ob- 
tained. The  ribs  serve  as  a  guide,  so  that  the  workman 
produces  the  proper  shape.  From  this  point  up  to  the  verti- 
cal, good  results  can  be  secured  with  the  ribs  attached,  to  the 
lagging.  Some  contractors  found  it  more  convenient  to  use 
ribs  that  were  connected  with  each  other  by  a  skeleton  frame- 
work only,  and  then  to  slip  the  lagging  in,  one  piece  at  a 
time.  For  some  of  the  sewers,  in  which  the  brick  lining  was 
not  carried  quite  up  to  the  spring  line,  a  separate  side  form 
of  skeleton  ribs  and  loose  lagging  was  set  upon  brace  legs 
bearing  on  the  bottom  of  the  invert.  This  form  carried  the 
concrete  from  about  2  ft.  below  to  about  2  ft.  above  the 
springing  line.  The  arch  ribs  then  became  segmental  and 
rested  upon  the  middle  braces.  This  method  has  the  ad- 
vantage of  using  ribs  that  are  lighter  and  more  easily  handled 
than  those  that  are  semi-circular.  For  arch  centering,  it  is 
necessary  and  convenient  to  use  independent  ribs  and  loose 
lagging,  for  the  centers  can  then  be  carried  forward  piece- 


'AQUEDUCTS    AND    SEWERS.  565 

meal,  the  falsework  upholding  the  green  arch  and  re-erected 
at  the  advance  end  of  the  work.  In  these  matters  each  con- 
tractor prefers  to  use  his  own  ingenuity,  and  so  long  as  the 
work  is  properly  built,  the  engineer  can  well  give  him  con- 
siderable latitude  as  to  use  of  methods.  One  thing,  however, 
the  engineer  must  insist  upon — that  all  centering  and  false- 
work be  as  nearly  rigid  as  possible.  Even  a  slight  settle- 
ment "of  the  centers  at  the  crown  under  the -load  of  concrete 
and  backfill  will  cause  the  arch  to  kick  out  at  the  quarters, 
and  if  the  green  concrete  arch  is  not  cracked  at  the  crown, 
it  will  be  crushed  on  the  inside,  about  half  way  between  the 
crown  and  springing  line.  A  reinforced  arch  is  no  more  im- 
mune to  this  danger  than  is  a  plain  concrete  arch.  How- 
ever, with  a  few  days  of  hardening,  although  the  damage 
may  be  serious,  the  danger  of  actual  collapse  is  less.  A  point 
to  be  guarded  against,  especially  in  reinforced  construction, 
is  any  foolish  act  on  the  part  of  contractor  or  workman,  due 
to  his  overconfidence  in  the  strength  of  the  structure  because 
it  contains  embedded  steel. 

The  mode  of  procedure  in  constructing  the  arch  ring  was 
to  erect  the  centers  with  lagging  complete.  The  lagging  was 
then  covered  with  building  paper  waterproofed  with  paraf- 
fine.  The  arch  reinforcing  bars  were  then  bolted  to  the  an- 
chor bars  and  the  longitudinals  connected  up.  The  lining  of 
Portland  cement  mortar  was  first  laid  on  the  lagging.  Be- 
fore this  mortar  had  set,  concrete  was  rammed  in  between  it 
and  the  sheeting  to  a  height  of  18  ins.  above  the  springing 
line,  and  then  the  remainder  of  the  concrete  placed  without 
outside  forms.  The  top  of  the  arch  ring  was  finally  finished 
with  a  i-in.  mortar  coat.  In  regard  to  the  concrete,  Mr. 
Parmley  remarks: 

"Concrete  will  flush  up  to  the  forms  and  produce  a  better 
surface,  and  the  voids  in  the  stone  will  be  much  better  filled 
if  it  is  so  wet  as  to  require  but  little  tamping ;  moreover  there 
is  less  danger  of  obtaining  a  weak,  porous  wall  should  a 
workman  neglect  thorough  tamping,  than  there  is  where  only 
a  moist  mixture  is  used.  It  is  also  to  the  contractor's  inter- 
est to  use  wet  concrete  for  much  less  labor  is  required  in  mix- 
ing and  placing  it.  Small  broken  stone  or  gravel  is  preferable 
in  concrete  for  sewers.  The  walls  being  comparatively  thin, 


566  CONCRETE    CONSTRUCTION. 

unless  there  be  a  considerable  excess  of  mortar,  if  coarse 
stones  are  used,  the  concrete  will  be  honey-combed  with 
voids.  The  stones  should  be  well  graded  in  size  from  large 
to  fine,  but  the  largest  fragments  should  not  exceed  il/2  ins. 
in  greatest  dimension." 

Cost. — A  number  of  records  of  cost  of  constructing  short 
sections  of  the  sewer  described  are  given  by  Mr.  Parmley,  as 
follows : 

Labor  placing  anchor  bars.  Per  day. 

i  man,  at  $3.50  $3.50 

i  man,  at  $1.75    « .. 1.75 

4  hours-  carrying  steel  at  20  cts 0.80 


$6.05 

The  anchor  bars   were  placed  for  40  lin.  ft.  of  sewer,  or 
about  1,504  Ibs.  of  metal  at  a  cost  of  0.4  ct.  per  Ib. 

The  concreting  gang  for  the  sides  consisted  of : 

5  men  wheeling  and  mixing  at  $1.75 $8.75 

i  man    tamping 1.75 

2-3  time  man  lowering  brick  and  concrete  at  $2.25.  . .  .  1.50 

i  man   carrying   concrete    1.75 


$13-75 

This  gang  built  the  side  wall  for  40  ft.  of  sewer  daily,  or 
13  cu.  yds.  Cost  of  labor  per  cu.  yd.  was,  therefore,  $1.06.  The 
concrete  was  tamped  behind  the  brick  lining  as  the  latter  was 
built  up  by  the  mason. 

Cost  of  single  ring  brick  lining  at  sides: 

2  masons  at  70  cents  per  hour. . . . . . . .  .t $11.20 

i  man  mixing  mortar 2.25 

1-3  time  man  lowering  at  $2.25   0.75 

3  men  wheeling  sand,  filling  buckets  and  dumping. . .  .       5.25 


Total  labor  for  40  lin.  ft.  of  sewer $1945 

Quantity  of  brick  masonry  laid,  cu.  yd 6.38 

Labor  per  cu.  yd 3.05 

An  account  was  kept  of  labor  performed  on  85  lin.  ft.  of 
arch  work,  or  14  1-6  ft.  daily.    The  force  was  as  follows: 


AQUEDUCTS    AND    SEWERS.  567 

1  man  putting  mortar  lining  on  centering  $1-75 

2  men  mixing  mortar,  screening  and  wheeling  sand.  .       3.50 

1  man   tamping  concrete    1.75 

8  men  on  mixing  board  at  $1.75 14.00 

$21.00 

No.  cu.  yd.  placed  daily 25.64 

Labor  per  cu.  yd 0.82 

Placing  centering  and  arch  bars: 

2  men  at  $1.75    $3.50 

i  man  at  $3.50 3.50 

$7.00 

Costs,  for  14  1-6  ft.  daily,  $0.49  per  lin.  ft. 

As  nearly  as  could  be  judged,  about  two-thirds  of  the  labor 
was  used  in  erecting  the  centering  and  one-third  in  putting 
the  steel  in  place.  The  amount  of  steel  placed  daily  was  785 
Ibs.,  at  cost,  therefore,  of  0.3  of  a  cent  per  lb.,  and  the  cost 
of  erecting  and  moving  centers,  $0.33  per  lin.  ft.  of  arch. 

Another  record  of  39.27  ft.  on  a  curve,  gave  for  the  cost  of 
the  brick  work  at  sides  the  same  result  as  above,  but  the  in- 
spector's record  of  men  working  on  concrete  backing  at  sides 
showed  a  less  cost,  as  follows : 

4  men  mixing  at  $1.75 $7.00 

2-3  time  man  lowering  at  $2.25 1.50 

i  man  in  bottom  1-75 


$10.25 

They  placed  12.7  cu.  yd.  at  a  cost  of  $0.81  per  cu.  yd. 

This  figure  probably  more  nearly  represents  the  average 
cost  than  the  $1.06  reported  in  the  first  instance. 

The  cost  of  placing  the  anchor  bars  on  straight  sewer,  rep- 
resenting average  progress,  at  another  time,  was  found  to  be : 

i  man » $3-5° 

i  man  , J-75 


$5-25 

They  placed  the  steel  for  44  ft.  of  sewer  or  1,650  lb.  at  a  cost 
of  0.32  of  a  cent  per  lb. 


568  CONCRETE    CONSTRUCTION. 

Further  notes  for  6  days'  work,  when  it  seemed  to  repre- 
sent as  nearly  as  possible  the  general  average  for  the  whole 
were: 

Labor  on  arch  concrete : 
Daily  progress  was  13  1-6  ft. 

The  force  employed  was: 

7  men  making  concrete,  at  $1.75 $12.25 

i  man  plastering  the  center 1.75 

i  man  mixing  mortar   2.00 

i  man  tamping 1.75 

$1775 
On  straight  arch  work  they  placed  24.1  cu.  yd.  daily  at  a 

.cost  of  $0.74  per  cu.  yd.     In  three  days'  work  on  a  curve,  the 

same  gang  placed  26.37  cu-  yd-  daily  at  a  cost  of  $0.675  per 

cu.  yd. 

On  centering  and  steel  for  arch,  three  men  kept  up  with 

the  regular  progress  of  the  arch-concreting  gang.     The  cost, 

therefore,  is: 

1  man    $3.50 

2  men  at  $1.75    3.50 

$7.00 

They  averaged  13  ft.  daily,  or  at  a  total  cost  of  about  $0.54 
per  lin.  ft.  of  sewer. 

Two-thirds  of  this  labor  was  on  the  centering  or  $0.36  per 
lin.  ft.  of  arch;  $0.18  per  lin.  ft.  placed  the  steel  ready  for  em- 
bedding, or  about  55.5  Ib.  per  ft.  of  arch,  at  a  cost  of  0.32  of  a 
cent  per  Ib. 

For  the  double  ring  brick  lining  at  the  bottom,  the  regular 
daily  rate  of  progress  was  28  ft.  or  11.15  cu-  yd.  with: 

2  bricklayers    $11.20 

5  men  at  $1.75 8.75 

i  man  at  $2.25    2.25 

$22.20 

or  at  a  cost  of  $1.98  per  cu.  yd.    This  is  given  only  because  it 
is  of  interest  in  connection  with  the  cost  of  the  concrete. 


AQUEDUCTS    AND    SEWERS.  569 

Other  observations  on  cost  of  placing  steel  skeleton  and 
concrete  did  not  vary  materially  from  the  figures  given.  It 
will  be  observed  that  no  charge  for  superintendence  or  any- 
thing for  the  general  expenses  is  included  in  the  estimates  of 
cost.  These  charges  were,  of  course,  impossible  to  obtain. 
On  another  contract  with  machine  mixing,  as  high  as  36  lin. 
ft.  of  13  ft.  6  in.  arch  were  built  in  a  day,  but  no  data  as  to 
cost  were  taken,  though  it  was  evidently  less  than  for  the 
work  with  hand-mixed  concrete. 

REINFORCED  CONCRETE  SEWER  AT  WILMING- 
TON, DEL. — Records  of"  a  notable  job  of  sewer  construction 
at  Wilmington,  Del.,  in  1903,  are  furnished  by  Mr.  T.  Chalkley 
Hatton.  The  sewer  was  built  by  day  labor  for  the  city;  its 
cross-section  at  various  points  is  shown  by  Fig.  265.  The 
cross-section  of  sewers  in  trenches  deep  enough  to  cover  the 
arch  are  marked  "deep  cutting" ;  the  sections  where  the  arch 
projects  above  the  ground  surface  are  marked  "light  cutting." 
The  section  through  the  marsh  was  700  ft.  long,  the  cutting 
being  8  ft.  deep,  and  at  high  tide  the  marsh  was  flooded  I  to  4 
ft.  The  material  was  a  soft  mud  that  would  pull  a  tight  rub- 
ber boot  from  a  workman's  foot.  The  cost  of  this  marsh 
excavation  including  cofferdams,  underdraining,  pumping, 
etc.,  wras  $4.60  per  cu.  yd.  For  1,100  ft.  the  9^  ft.  sewer  was 
through  a  cut  22  to  34  ft.  deep,  the  material  being  clay  under- 
laid by  granite.  A  Carson-Lidgerwood  cableway  was  used. 
Although  the  crown  of  the  arch  was  but  8  ins.  thick,  it  with- 
stood the  shock  of  dumping  I  cu.  yd.  buckets  of  earth  and 
rock  from  heights  of  3  to  10  ft. ;  and  the  weight  of  25  ft.  of 
loose  filling  caused  no  cracks  in  the  concrete. 

Concrete  was  placed  in  4-in.  layers  (the  depth  of  the  lag- 
ging) and  well  rammed,  since  it  was  found  that  "wet"  con- 
crete left  small  honeycombed  spaces  on  the  inner  surface. 
Concrete  for  the  invert  was  1-2-6,  the  stone  being  i^-in. 
and  smaller,  and  the  sand  being  crusher  dust.  The  arch 
was  1-2-5. 

The  reinforcing  metal  used  in  the  9^-ft.  sewer  was  No.  6 
expanded  metal,  6-in.  mesh,  in  sheets  8x5^  ft.,  supplied  by 
Merritt  &  Co.,  of  Philadelphia.  A  single  layer  was  placed 
around  the  sewer,  2  ins.  from  the  inner  surface,  its  position 


570 


CONCRETE    CONSTRUCTION. 


being  carefully  maintained   by  the  men  ramming,  and  with 

but  little  difficulty  as  the  sheets  were  first  bent  to  the  radius 

of  the  circle.     Each  sheet  was  lapped  one  mesh  (6  ins.)  over 

I 

Fbrtlcmet  Concrete , 


Portland  Concrete 
Wire  Woven  Mesh 


"Wire  Woven  Mesh 


Broken  Stone 


Section  in  Light  CutKng 


Section  in  Deep  Cutting. 

Jl*—,.^  Pbrtlotnd  Concrete- 

fitrtbnd  Concretv^f^^^^-wire  Woven  Mesh 


f* 

Section  in  Light  Cuth'no; 


T.C.Pip* 

'->| 

Section  in  Deep  Cutting. 


Section  in  Deep  Cuttinof 


Section  throucjh   Marsh. 
Fig.  265.—  Cross-  Sections   of  Sewer  at  Wilmington,  Del. 

its  neighbor  at  both  ends  and  sides,  and  no  sheets  were  wired 
except  the  top  ones,  which  were  liable  to  displacement  by  men 
walking  over  them. 


AQUEDUCTS    AND    SEWERS.  571 

The  metal  used  on  the  rest  of  the  work  was  a  wire-woven 
fabric  furnished  by  the  Wight-Easton-Townsend  Co.,  of  New 
York.  This  fabric  comes  in  rolls  5^  ft.  wide  and  100  ft.  to 
the  roll.  The  wire  is  No.  8,  with  a  6  x  4-in.  mesh.  This  fabric 
was  placed  by  first  cutting  the  sheets  to  the  required  length 
to  surround  the  sewer  entirely,  embedding  it  in  the  concrete 
as  fast  as  concrete  was  placed,  in  the  same  manner  as  was 
done  with  the  expanded  metal  except  over  the  center  where, 
on  account  of  its  pliability,  the  fabric  was  held  the  proper  dis- 
tance from  the  lagging  by  a  number  of  2-in.  blocks  which 
were  removed  as  the  concrete  was  placed.  The  wire  cloth, 
being  all  in  one  sheet,  can  be  placed  a  little  more  expeditiously 
than  expanded  metal,  but,  on  the  other  hand,  the  expanded 
metal  holds  its  position  better  in  the  concrete,  since  it  is  more 
rigid. 

We  quote  now  from  Mr.  Hatton's  letter :  "The  major 
portion  of  concrete  was  mixed  by  machine  at  a  cost  of  66  cts. 
per  yard,  including  wheeling  to  place,  coal  and  running  of 
mixing  machine,  wages  being  $1.50  per  day  of  8  hrs,  Stone 
was  delivered  alongside  of  machine  and  all  material  had  to 
be  wheeled  in  barrows  upon  the  platform,  and  after  mixing 
to  the  sewer.  Placing  and  ramming  concrete  around  the 
forms  cost  39  cts.  per  cu.  yd.,  additional.  Setting  forms  in 
invert  cost  2  cts.  per  cu.  yd.,  setting  centers  7  cts.  per  cu.  yd. 
Cost  of  setting  forms  and  centers  includes  placing  steel  metal. 
Each  lineal  foot  of  9^4 -ft.  sewer  contained  i  cu.  yd.  of  con- 
crete, although  the  section  only  calls  for  0.94  cu.  yd.  The 
excess  was  usually  wasted  by  falling  over  sides  of  forms 
or  being  made  too  thick  at  crown. 

"This  yard  of  1-2-5  concrete  cost  in  place  as  follows 
(record  taken  as  an  average  of  several  days'  run)  : 

Cement,  1.31  bbls.  at  $1.30. $i-7°3 

Stone,  0.84  cu.  yds.  at  $1.21 1.016 

Stone  dust,  0.42  cu.  yd.  at  $1.21 0.508 

Labor  at  18^  cts.  per  hour 0.987 

Labor  setting  forms  and  setting  metal 0.045 

Cost  of  forms  (distributed  over  1,800  ft.  of  sewer) 0.082 

40  sq.  ft.  expanded  metal  at  4%  cts 1.700 

Labor   plastering   invert 0.070 

Cost  per  ft.,  or  per  cu.  yd $6.m 


572  CONCRETE    CONSTRUCTION. 

"The  forms  for  the  invert  were  made  of  2-in.  rough  hem- 
lock boards  cut  out  4  ins.  less  diameter  than  the  diameter 
of  the  sewer,  except  for  18  ins.  at  the  bottom  of  the  form 
which  coincided  with  the  inside  form  of  sewer.  The  bottom 
of  the  sewers  was  laid  to  the  bottom  of  this  form  before 
it  was  set.  Then  the  lagging,  consisting  of  2  x  6-in.  x  i6-ft. 
hemlock  planed,  was  placed  against  each  side  of  the  form, 
one  at  a  time,  and  the  concrete  brought  to  the  line  of  this 
top  in  6-in.  layers  until  the  whole  invert  was  finished.  These 
forms  were  set  in  i6-ft.  sections,  five  to  each  section. 

"The  centers  consisted  of  seven  ribs  of  2-in.  hemlock  upon 
which  was  nailed  i^-in.  lagging,  2  ins.  wide,  tongued  and 
grooved,  and  were  16  ft.  long,  non-collapsible,  but  had  one 
wing  on  each  side,  9  ins.  wide,  which  could  be  wedged  out 
to  fit  any  inaccuracies  in  the  invert.  We  used  four  of  these 
centers  setting  two  at  each  operation  and  worked  from  two 
ends.  We  left  the  centers  in  for  18  hours  before  drawing. 

"The  cost  of  the  concrete  on  the  smaller  sewers  was  the 
same  as  are  the  larger  sewers,  but  the  steel  metal  cost  less, 
as  it  was  wire  woven  metal  that  cost  2l/2  cts.  per  sq.  ft.  It 
was  much  easier  handled  and  cut  to  no  waste  as  it  came  in 
long  rolls  and  was  very  pliable. 

"After  training  our  men,  which  occupied  about  one  week 
or  10  days,  we  had  no  difficulty  in  getting  the  concrete  well 
placed  around  the  metal,  preserving  the  proper  location  of  the 
latter,  which,  however,  bore  constant  watching,  as  a  careless 
workman  would  often  take  the  temporary  supporting  blocks 
and  allow  the  metal  to  rest  against  the  wooden  center,  in 
which  case  the  metal  would  show  through  the  surface  insicte 
of  the  sewer.  The  metal  was  kept  2  ins.  away  from  the  inside 
forms  and  the  arch.  To  keep  it  at  this  location  we  had  sev- 
eral 2-in.  wooden  blocks  cut  which  were  slipped  under  the 
wire  or  expanded  metal  and  as  soon  as  some  concrete  was 
pushed  under  the  wire  at  this  point  the  block  was  removed. 

"After  the  forms  were  removed  the  invert  needed  plaster- 
ing, but  the  arch  was  practically  like  a  smoothly  plastered 
wall  except  where  it  joined  the  invert,  where  it  frequently 
showed  the 'result  of  too  much  hurry  in  depositing  the  first 


AQUEDUCTS    AND    SEWERS.  573 

\oads  of  concrete  on  the  arch.  We  remedied  this  by  requiring 
less  concrete  to  be  deposited  at  the  start,  thus  giving  the 
rammers  time  to  place  the  material  properly. 

"An  interesting  result  was  obtained  in  the  smoothness  of 
the  inside  surface  by  using  a  mixture  of  different  sized  stones. 
When  24-in.  stones  or  smaller  were  used  in  the  arch,  the  in- 
side was  honeycombed;  but,  where  I  to  i^-in.  stones 
(nothing  smaller)  were  used,  the  inside  was  perfectly  smooth, 
and  the  same  was  true  of  the  invert,  showing  that  the  use  of 
larger  stones  is  an  advantage  and  secures  more  monolithic 
work.  When  the  run  of  the  crusher  from  il/2  to  %-in.  stones 
was  used  the  work  was  not  at  all  satisfactory. 

"The  difference  in  cost  of  mixing  by  hand  and  machine  is 
practically  nothing  on  this  kind  of  work.  As  the  moving  of 
the  machine  to  keep  pace  with  the  progress  of  the  work  equals 
the  extra  cost  of  mixing  by  hand  when  the  mixing  can  be 
done  close  to  the  point  where  the  cement  is  being  placed." 

The  total  cost  of  the  sewers,  including  excavation,  etc., 
was: 

Cost  per  lin.  ft. 

9*4 -ft.  sewer  through  marsh   $32.00 

9*4 -ft.  sewer  in  cut  averaging  24^/2   ft 24.00 

6l/2-ii.  sewer,  in  cut  averaging  12  ft 10.00 

5 -ft.  sewer  in  cut  averaging  I il/2  ft 6.70 

SEWER  WITH  MONOLITHIC  INVERT  AND 
BLOCK  ARCH.— The  following  records  of  construction  for 
a  sewer  built  at  Coldwater,  Mich.,  in  1901,  are  given  by  Mr. 
H.  V.  Gifford.  The  sewer  had  a  monolithic  invert  and  a 
block  arch. 

The  sewer  was  circular,  having  an  inner  diameter  of  42  ins., 
the  thickness  of  the  invert  and  the  arch  alike  was  8  ins.  Fig- 
ure 266  is  a  cross-section.  The  concrete  was  i  of  Portland 
cement  to  6  of  gravel.  There  were  n  concrete  blocks  in  the 
ring  of  the  arch,  each  block  being  24  ins.  long,  8  ins.  thick, 
8  ins.  wide  on  the  outside  of  the  arch  and  5^4  ins-  wide  on  the 
inside  of  the  arch.  A  block  weighed  90  Ibs.  which  was  too 
heavy  for  rapid  laying;  blocks  18  ins.  long  would  have  been 
better.  Some  8,500  blocks  were  made.  Molds  were  of  2-in. 
lumber,  lined  with  tin,  for  after  a  little  use  it  was  found  the 


574 


CONCRETE    CONSTRUCTION. 


concrete  would  stick  to  the  wood  when  the  mold  was  re- 
moved. The  four  sides  of  the  mold  formed  the  extrados,  the 
intrados,  and  the  two  ends  of  the  block ;  the  other  two  sides 
being  left  open.  When  put  together  the  mold  was  laid  upon 
a  i -in.  board,  12x30  ins.,  reinforced  by  cleats  across  the 
bottom.  The  sides  of  the  molds  were  held  together  with 
screws  or  wedge  clamps.  When  the  blocks  had  set,  the  sides 
of  the  molds  were  removed,  and  the  blocks  were  left  on  the 
i2x3O-in.  boards  for  3  days,  then  piled  up,  being  watered 
several  times  each  day  for  a  week. 

A  gang  of  14  men  made  the  blocks ;  2  screening  gravel 
through  i-in.  mesh  screen;  4  mixing  concrete;  4  molders ;  3 
shifting  and  watering  blocks,  and  I  foreman.  With  a  little 


,i  -- 

: 


Harrcf  Cement  Corrcr. 
'/?/,  3  sarrcf,  6.-av*t 


Fig.  266.— Sewer  with  Monolithic  Invert  and  Block  Arch. 

practice  each  molder  could  turn  out  175  blocks  a  day;  and 
since  each  block  measured  ^4  cu.  ft.,  the  output  of  the  14  men 
was  K)l/2  cu.  yds.  a  day.  Mr.  Gifford  informs  us  that  the 
wages  were  $1.50  a  day  for  all  the  men,  except  the  foreman. 
The  daily  wages  of  the  14  men  were  $22,  so  that  the  labor 
of  making  the  blocks  was  $i.io  per  cu.  yd. 

Each  batch  of  concrete,  containing  l/2  bbl.  of  .Portland  ce- 
ment costing  $1.35  per  bbl.,  made  18  blocks,  (i  bbl.  per  cu. 
yd.)  Since  the  gravel  cost  nothing,  except  the  labor  of  screen- 
ing it,  the  total  cost  of  each  block  was  n  to  12  cts.,  which 
includes  0.85  cent  for  use  of  molds  and  mold  boards,  which 
were  an  entire  loss.  At  12  cts.  per  block  the  cost  was  $4.32 
per  cu.  yd. 


AQUEDUCTS    AND    SEWERS.  575 

The  contract  price  was  $3  per  lin.  ft.  of  this  sewer,  as 
against  a  bid  of  $3.40  per  ft.  for  a  brick  sewer. 

When  the  trenching  had  reached  to  the  level  of  the  top  of 
the  invert,  two  rows  of  stakes  were  driven  in  the  bottom, 
stakes  being  6  ft.  apart  in  each  row,  and  rows  being  a,  dis- 
tance apart  %-in.  greater  than  the  outer  diameter  of  the 
sewer.  These  stakes  were  driven  to  such  a  grade  that  the  top 
of  a  2x4~in.  cap  or  "runner"  set  edgewise  on  top  of  them 
was  at  the  proper  grade  of  the  top  of  the  invert.  The  excava- 
tion for  the  invert  was  then  begun,  and  finished  to  the  proper 
curve  by  the  aid  of  a  templet  drawn  along  the  2  x  4-in.  run- 
ners. In  gravel  it  was  impossible  to  hold  the  true  curve  of 
the  invert  bottom.  Concrete  was  then  placed  for  the  invert. 
To  hold  up  the  sides  of  the  invert  concrete,  a  board  served 
as  a  support  for  the  insides,  but  regular  forms  were  more 
satisfactory  in  every  respect  except  that  they  were  in  the  way 
of  the  workmen.  A  form  was  tried,  its  length  being  6  ft.  It 
was  built  like  the  center  for  an  arch,  except  that  the  sheeting 
was  omitted  on  the  lower  part  of  the  invert.  It  was  suspend- 
ed from  the  cross-pieces  resting  on  the  "runners."  After 
the  concrete  had  been  rounded  in  place,  the  form  was  removed 
and  the  invert  trued  up.  This  form  worked  well  in  soil  that 
could  be  excavated  a  number  of  feet  ahead,  so  that  the  forms 
could  be  drawn  ahead  instead  of  having  to  be  lifted  out ;  but 
in  soil,  where  the  concreting  must  immediately  follow  the 
excavation  for  the  invert,  the  form  is  in  the  way.  The  invert 
was  trued  up  by  drawing  along  the  runners  a  semicircular 
templet  having  a  radius  of  21^2  ins.  Then  a  y2-m.  coat  of 
1-2  mortar  was  roughly  troweled  on  the  green  concrete. 
Another  templet  having  a  2i^in.  radius  was  then  drawn 
along  the  runners  to  finish  the,  invert. 

When  the  plaster  had  hardened,  two  courses  of  concrete 
blocks  were  laid  on  each  shoulder  of  the  invert,  using  a 
1-2-14  mortar,  the  y\  part  being  lime  paste.  The  lime  made 
the  mortar  more  plastic  and  easier  to  trowel.  Then  the  form 
for  the  arch  was  placed,  and  as  each  8-ft.  section  of  the  arch 
was  built,  a  grout  of  i-i  mortar  was  poured  over  the  top  to  fill 
the  joints.  Earth  was  thrown  on  each  shoulder  and  tamped, 
and  the  center  moved  ahead. 


576 


CONCRETE    CONSTRUCTION. 


Common  laborers  were  used  for  all  the  invert  work,  except 
the  plastering  which  was  done  by  masons  who  were  paid 
30  cts.  per  hr.  Masons  were  also  used  to  lay  the  concrete 
blocks  in  the  arch.  Mr.  Gifford  states  that  two  masons  would 
lay  at  the  rate  of  100  lin.  ft.  of  arch  per  day,  if  enough  invert 
were  prepared  in  advance.  As  there  were  n  blocks  in  the 
ring  of  the  arch,  this  rate  would  be  equivalent  to  7^  cu.  yds. 
of  arch  laid  per  mason  per  day. 


Plan  Showing  Arrangement  of  I  Beams  and  Cover. 


Sec-Hon  C-D. 
Fig.  267.— Concrete  Block  Manhole. 


Section  A-D. 


COST  OF  BLOCK  MANHOLES.— The  following  costs 
of  constructing  concrete  block  manholes  for  electric  conduit 
at  Rye,  N.  Y.,  were  recorded  by  Mr.  Hugh  C.  Baker,  Jr. 
The  arrangement  of  the  blocks,  their  size  and  shape  and  the 
dimensions  of  the  completed  manholes  are  shown  by  Fig.  267. 
The  blocks  were  molded  of  1-2-5  %-in.  broken  stone  concrete 
in  30  wooden  molds  made  by  a  local  carpenter  at  a  cost  of 
from  $3.50  to  $12  each.  The  concrete  was  placed  in  the  molds 
very  wet,  with  very  little  tamping,  and  was  allowed  to  set 
for  seven  days  before  the  blocks  were  moved  to  the  work. 


AQUEDUCTS    AND    SEWERS. 


577 


The  molds  were  left  in  place  from  24  to  36  hours.  With  the 
facilities  at  hand  six  complete  sets  of  top  blocks  were  made 
each  day  by  four  men,  when  no  wall  blocks  were  being  made, 
and  half  a  set  (15)  wall  blocks  and  two  sets  of  top  blocks 
were  made  each  day  by  four  men.  The  cost  of  the  block 
manholes  complete  was  as  follows,  per  manhole : 

30  wall   blocks,   2^/2   cu.   yds $21.00 

6  cover  blocks,   il/2   cu.  yds.   reinforced 4.27 

I-beams  for  cover,  in  place 5.40 

Supervision,  freight,  hauling  5.6  tons  concrete 9.38 

Labor  placing  cover,  3  hrs.  at  15  cts 0.45 

Labor  placing  walls,  20  hrs.  at  15  cts 3.00 

Total,  exclusive  of  iron  cover $43-5o 

CEMENT  PIPE,  CONSTRUCTED  IN  PLACE.— In  con- 
structing 8-in.  cement  sewer  for  the  Foster  Armstrong  Piano 
Co.'s  works  at  Rochester,  N.  Y.,  a  gang  of  seven  men  aver- 
aged 300  ft.  of  pipe  per  lo-hour  day,  using  a  Ransome  pipe 
mold.  The  mold  is  shown  by  Fig.  268.  It  is  made  of  sheet 
steel,  with  an  inner  core  10  ft.  long,  the  front  end  of  which, 
is  surrounded  with  a  sheet  steel  shell  that  serves  as  an  outer 
form  for  the  pipe.  The  mortar  mixed  rather  dry  was  packed 
into  the  annular  space  between  core  and  shell  by  one  man, 
using  a  short  wooden  rammer.  A  second  man  kept  the  mold 
slowly  moving  forward  by  operating  the  lever,  which  by 
means  of  a  ratchet  and  drum  winds  up  a  wire  rope  stretched 
ahead  to  a  deadman  in  the  trench  bottom.  As  the  mold  moves 
ahead  it  leaves  behind  it  the  cement  pipe.  A  third  man  care- 
fully filled  under  the  invert  and  over  the  haunches  of  the 
green  pipe  with  earth  to  give  it  support.  The  following  was 
the  itemized  cost  per  day,  300  ft.  of  pipe  laid : 

6  men  at  $1.70  per  lo-hour  day $10.20 

I   foreman    3-°° 

3  bbls.  cement   at  $1.25 375 

3.3  cu.  yds.  sand  at  85  cts 2.80 

Water 0.15 

Total  for  300  lin.  ft $19-9° 

This  is  equivalent  to  6.63  cts.  per  lin.  ft.  of  pipe. 


578 


CONCRETE    CONSTRUCTION. 


In  Trans.  C.  E.,  Vol.  31,  1894,  p.  153,  James  D.  Schuyler 
gives  the  cost  of  cement  pipe  made  by  the  Ransome  system 
for  the  Denver  Water  Works.  There  is  a  wrought  iron  shell 


Fig.  268.— Ransome  Continuous  Mold  for  Concrete  Pipe  Construction. 

of  the  size  of  the  inner  diameter  of  the  pipe  forming  the  inner 
mold.  To  this  shell  is  attached  a  "leader"  and  "saddle" 
of  larger  diameter  forming  the  outer  mold.  These  molds  are 


AQUEDUCTS    AND    SEWERS.  579 

drawn  slowly  along  the  trench  by  a  cable  and  horse  whim, 
and  the  concrete  is  shoveled  continuously  into  the  core  space 
between  the  molds  and  rammed  on  a  long  incline.  The  top 
half,  or  arch,  of  the  pipe  is  supported  by  sheet  iron  plates 
(2  ft.  wide),  placed  one  after  another  on  the  forward  end  of 
the  mold ;  and,  being  clamped  together  at  the  top  and  sides, 
remain  in  position  after  the  mold  is  slid  out  from  under  them. 
After  the  mold  has  passed  along,  these  iron  plates  are  sup- 
ported by  upright  sticks  and  by  horizontal  clamping  rods. 
The  plates  are  left  in  place  for  24  to  48  hrs.  The  concrete, 
made  1-3 1/2,  river  sand  and  gravel,  was  machine  mixed.  A 
gang  of  30  men  mixed,,  wheeled,  shoveled  and  tamped  the  con- 
crete, attended  to  the  plates,  cleaning  and  greasing  them,  etc. 
This  gang  would  make  short  runs  at  the  rate  of  900  lin.  ft. 
of  pipe  a  day,  but  counting  stoppages,  the  average  rate  was 
300  ft.  a  day.  The  inner  diameter  of  the  pipe  was  38  ins., 
and  its  bottom  was  molded  flat  for  a  width  of  18  ins.  The 
concrete  shell  was  2l/2  to  3  ins.  thick.  The  pipe  was  washed 
with  pure  cement  grout,  applied  with  brushes  after  removing 
the  iron  plates.  With  cement  at  $3.75  per  bbl.,  gravel  at  $1.25 
per  cu.  yd.,  and  labor  at  $1.75  to  $2  per  day,  the  cost  of  this 
pipe  was  $1.35  to  $1.50  per  ft.,  after  the  gang  was  well 
organized. 

PIPE  SEWER,  ST.  JOSEPH,  MO.— In  constructing  ex- 
tensions to  36-111.,  42-in.,  48-in.  and  72-in.  sewers  at  St.  Joseph, 
Mo.,  reinforced  concrete  pipe  of  the  form  shown  by  Fig.  269 
was  employed.  The  thickness  of  shell  for  the  various  sizes 
was  4  ins.,  4^  ins.,  5  ins.,  and  7  ins.  All  sizes  were  made 
in  3-ft.  lengths,  one  end  of  which  is  rebated  and  beveled  to 
form  a  spigot  and  the  other  end  of  which  is  chamfered  on  the 
inner  edge  to  receive  the  bevel  of  the  spigot.  This  jointing 
leaves  a  circumferential  groove,  into  which  the  hooked  ends 
of  the  longitudinal  reinforcing  bars  project  in  such  a  way  that 
a  circular  hoop  can  be  threaded  through  them  to  connect  suc- 
cessive lengths.  The  reinforcement  is  of  the  same  form  for 
all  sizes  of  pipe,  but  seven  longitudinals  were  used  in  the 
72-in.  size  and  five  for  all  smaller  sizes;  the  circumferential 
bars  were  in  all  cases  spaced  one  9  ins.  from  each  end.  The 
pipe,  as  described,  is  the  standard  pipe  made  by  the  Rein- 


580  CONCRETE    CONSTRUCTION. 

forced  Concrete  Pipe  Co.,  of  Jackson,  Mich.,  and  is  covered 
by  patents.  The  practice  of  this  company  is  to  manufacture 
the  pipe  itself  on  the  ground  and  furnish  it  to  the  contractor. 
It  does  not  contract  to  build  sewers  nor  does  it  dispose  of 
rights  to  manufacture  to  contractors. 

Pipe  Molding. — The  pipe  is  molded  endwise.  A  bottom 
plate  so  shaped  as  to  form  the  hub  or  receiving  end  of  the  pipe 
is  set  up.  On  the  upper  or  inner  flange  of  this  cast  iron  bot- 
tom plate  is  set  the  core  defining  the  inside  diameter  of  the 
pipe ;  this  core  is  in  four  segments  of  sheet  steel.  The  longi- 
tudinal reinforcing  bars  are  next  inserted  in  slots  in  the  bot- 


) 


Fig.  269. — Jackson  Concrete  Sewer  Pipe. 


torn  plate  and  the  outside  form  of  sheet  steel  is  then  set  up 
on  the  lower  and  outer  flange  of  the  bottom  plate.  Spacing 
clips  on  the  top  edge  of  the  outer  shell  hold  the  tops  of  the 
reinforcing  bars  in  position.  The  concrete  is  then  shoveled 
into  the  annular  mold  and  tamped  until  it  reaches  the  level 
for  the  first  circumferential  reinforcing  bar;  this  is  then 
placed  by  removing  the  spacing  clips,  threading  the  hoop  over 
the  longitudinal  bars  and  sliding  it  down  to  position.  Filling 
and  tamping  then  proceeds  until  the  second  hoop  is  to  be 
placed ;  this  is  placed  exactly  like  the  first,  and  filling  and 
tamping  then  proceeds  until  the  mold  is  filled.  At  the  St. 


AQUEDUCTS    AND    SEWERS.  581 

Joseph  work  a  1-2-3  mixture,  with  crushed  limestone  aggre- 
gate ranging  from  pea  size  to  i-in.  stone  was  used.  The  mold- 
ing was  done  in  tents  which  were  heated  by  coke  fires  in  sala- 
manders in  freezing  weather. 

Pipe  Laying. — In  laying,  the  pipes  are  handled  and  lowered 
into  position  just  as  are  cast  iron  water  pipe.  Successive 
lengths  are  placed  by  inserting  the  spigot  ends  into  the  cham- 
fered hub  ends  and  then  threading  the  tie  hoop  through  the 
hooked  ends  of  the  projecting  longitudinal  reinforcing  bars. 
A  strip  of  galvanized  iron  is  then  passed  under  the  pipe  and 
bent  up  so  as  to  girdle  the  circumferential  groove  except  for 
a  space  at  the  top;  the  groove  is  then  poured  with  a  wet  1-2 
cement  mixture,  which,  when  hardened,  completes  the  joint. 

COST  OF   MOLDING   SMALL   CEMENT   PIPE.— Mr. 

Albert  E.  Wright  gives  the  following  account  of  the  method 
and  cost  of  molding  and  laying  6  to  12-in.  cement  pipe  for 
irregular  work  at  Irrigon,  Ore. :  The  pipe  was  6  to  12  ins. 
inside,  made  of  Portland  cement  and  clean,  sharp  sand  of  all 
sizes  up  to  very  coarse.  The  mortar  was  mixed  rather  dry, 
but  very  thoroughly,  using  14.1  cu.  ft.  of  sand  to  I  bbl.  of 
cement,  or  very  closely  a  I  to  4  mixture.  From  six  to  seven 
buckets  of  water  were  used  to  each  barrel  of  cement,  except 
for  the  6-in.  pipe,  for  which  the  mortar  had  to  be  made  some- 
what stiffer  in  order  to  remove  the  inner  form,  which  was  not 
made  collapsible  as  in  the  larger  sizes. 

The  forms  were  sheet  iron  cylinders  with  a  longitudinal 
lap  joint  that  could  be  expanded  after  molding  the  pipe,  and 
removed  without  injuring  the  soft  mortar.  The  inner  form 
was  self-centering,  so  that  there  was  little  variation  in  the 
thickness  of  the  pipe. 

Four  men  were  required  in  making  cement  pipe  by  hand; 
one  mixed  the  mortar,  and  wheeled  it  to  the  place  of  work; 
another  threw  it  into  the  form  a  little  at  a  time  with  a 
hand  scoop;  a  third  rammed  it  with  a  tamping  iron,  and  a 
fourth  kept  the  new  pipe  sprinkled,  and  applied  a  coat  of  neat 
cement  slurry  to  the  inside  when  it  was  sufficiently  hard.  In 
molding,  the  form  of  the  bell  at  the  bottom  was  secured 
by  an  iron  ring  that  was  first  dropped  into  the  form,  and  the 
reverse  or  convex  form  at  the  top  was  made  with  a  second 


582  CONCRETE    CONSTRUCTION. 

ring.  While  still  in  its  form  the  pipe  was  rolled  or  lifted  into 
its  place  in  the  drying  yard,  and  the  form  was  then  carefully 
removed.  A  very  slight  blow  in  removing  the  form  would 
destroy  the  pipe,  and  a  considerable  number,  especially  of  the 
larger  sizes,  collapsed  in  this  way,  and  had  to  be  remolded. 
To  avoid  handling,  the  pipe  was  stacked  on  end  a  few  feet 
from  the  place  of  mixing,  the  form  being  moved  as  the  yard 
filled  with  pipe.  One  crew  of  four  men  could  make  about 
250  joints  or  500  lin.  ft.  of  pipe  a  day. 

As  soon  as  hard  enough,  the  pipe  was  turned  end  for  end, 
and  was  then  kept  wet  for  several  weeks  before  being  laid. 
The  coating  of  neat  cement  on  the  inside  was  applied  with  a 
short  whitewash  brush,  and  was  a  small  item  in  the  cost. 

In  laying,  the  trench  was  carefully  finished  to  grade  in 
order  to  have  the  joints  close  nicely,  and  the  ends  were  well 
wet  with  a  brush.  The  mason  then  spread  mortar,  mixed  I  to 
2,  on  the  end  of  the  pipe,  and  laid  a  bed  of  mortar  at  the  bot- 
tom of  the  joint.  He  then  jammed  the  section  into  place,  and 
swabbed  out  the  inside  of  the  joint  with  a  stiff  brush,  to  insure 
a  smooth  passage  for  the  water.  A  band  or  ring  of  mortar 
was  spread  round  the  outside  of  the  joint  as  an  additional 
reinforcement.  One  barrel  of  cement  would  joint  about  300 
sections  of  pipe.  The  materials  cost  as  follows :  Portland 
cement,  per  bbl.,  $4.45 ;  labor,  per  day,  $2 ;  foremen,  per  day, 
$2.50  to  $3;  hauling,  per  load  mile  (i  cu.  yd.),  20  cts. ;  sand, 
free  at  pit;  water,  free. 

The  pipe  was  all  of  a  1-4  sand  and  cement  mortar,  and  the 
amount  of  cement  in  one  foot  of  pipe  was  arrived  at  by 
assuming  that  where  the  sand  has  voids  in  excess  of  the  ce- 
ment used,  the  mortar  will  occupy  i.i  (see  Chapter  II)  times 
the  space  of  the  dry  sand,  which  yields  the  following  formula : 

Where— 

c  =r  cost  per  bbl.  of  cement,  or  $4.45. 

n  =  cu.  ft.  in  one  bbl.  (taken  at  3.5  here). 

j  =  ratio  of  sand  to  cement,  or  4. 

t/  —  inside  diameter  in  inches. 

t  =  thickness  of  pipe  in  inches. 

/  =  length  of  pipe  considered,  or  i  ft.  here. 


AQUEDUCTS    AND    SEWERS.  '  583 

Then  : 

cX'tXirX  (dt  +  t*) 

Cement-cost  per  foot  =  -  —  ,  which  gives 

n  X  s  X  i.i  X    144 
4-45  X  i  X  3-142    (dt  +  t2) 

here  =  -  =  o.co5j/  (dt  +  /2J- 

3.5  X  4  X  /.i 


This  gave  the  following  cement  costs  per  lineal  foot: 

Diameter,  Thickness,  Cost 

ins.                                                       ins.  per  foot. 

6    .....................              ilA  $0.0571 

8    .....  .  ...............             IJ4  0.0730 

10    .........  ............             \y%  0.0998 

12  .....................         \y2  0.1278 

The  sand  cost  was  based  on  15  cts.  per  cubic  yard  for  load- 
ing, and  a  haul  of  two  miles  of  i  cu.  yd.  to  the  load,  making 
five  trips  per  day,  at  $4  for  man  and  team.  It  bears  a  con- 
stant ratio  to  cement  cost,  being  11.2  per  cent,  of  the  cement 
cost.  The  labor  cost  of  making  was  based  on  the  foreman's 
estimate  that  a  foreman,  tamper,  mortar  mixer,  and  water 
man  should  finish  250  joints  a  day  of  6  or  8-in.  pipe.  For  the 
10  and  i2-in.  pipe,  the  labor  was  assumed  to  be  greater  in 
proportion  to  the  material.  The  foreman  was  taken  at  $3,  one 
man  at  $2.50  and  two  at  $2.  The  cement  for  painting  the 
inside  was  neglected.  Hauling  the  pipe  to  place  was  taken  at 
twice  the  cost  of  hauling  the  sand  per  mile,  and  a  haul  of  4 
miles  was  assumed.  The  cost  of  laying  was  based  on  a  fore- 
man's estimate  of  2  cts.  per  foot  for  trench,  and  that  one  man 
to  lay,  one  man  to  plaster  the  joints,  one  helper  and  one  man 
to  backfill  would  lay  600  ft.  per  day  of  6  or  8-in.  pipe.  The 
larger  sizes  were  assumed  to  cost  more  in  proportion  to  their 
material. 

These  various  costs  gave  the  following  results  for  small 
size  pipe  : 


CONCRETE    CONSTRUCTION. 


pipe. 

Cement    $0.057 

Sand    0.006 

Labor    0.019 

Hauling    0.024 

Laying    0.024 

Trench    ,  0.020 


Cost  per  foot  for- 

6-in. .         8-in.  lo-in. 

pipe.  pipe. 

$0.073        $0.099 
0.008 
0.019 
0.032 
0.024 

0.02O 


12-m. 
pipe. 
$0.128 
0.014 
0.034 
0.056 
0.042 

0.020 


Totals  $0.15          $0.176        $0.232        $0.294 

The  above  costs  show  that  the  pipe  in  place  costs  about 
twice  as  much  as  pipe  in  the  yard,  even  with  cement  at  $4.45. 


^ ,  yn^Ns?^^^ 

'   '-^lii^iii^^^ 


'     *TC<L      S.«T^ 

Fig.  270. — Bordenave  Pipe  for  Swansea,  England,  Water  Works. 

MOLDED  PIPE  WATER  MAIN,  SWANSEA,  ENG- 
LAND.— As  a  good  example  of  foreign  practice  in  molded 
pipe  conduit  work  a  water  main  constructed  at  Swansea,  Eng- 
land, has  been  selected.  This  pipe  line  had  to  operate  under  a 
head  of  185  ft. ;  it  was  constructed  under  the  patents  of  the 
French  engineer,  Mr.  R.  Bordenave,  who  has  built  many 
miles  of  the  same  type  of  conduit  on  the  Continent. 

Fig.  270  shows  the  construction  of  the  pipe,  the  drawing 
being  a  part  longitudinal  section  through  the  shell  at  the 
joint.  The  pipe  consists  of  an  inner  and  an  outer  reinforce- 
ment separated  by  a  sheet  steel  tube  and  all  embedded  in  a  1-2 
mortar.  Both  inner  and  outer  reinforcements  consists  of 
longitudinal  bins  of  cruciform  (+)  section  wound  by  a  spiral 
bar  of  the  same  section  wired  to  them  at  every  intersection. 
Only  the  outer  reinforcement  and  the  steel  tube  are  consid- 
ered in  calculating  the  strength  of  the  pipe,  the  inner  rein- 
forcement being  considered  as  simply  supporting  the  mortar. 


AQUEDUCTS    AND    SEWERS. 


585 


Fabrication  of  Reinforcement. — The  steel  tube  is  made  of 
i  mm.  (0.04  in.)  thick  sheets  of  steel  bent  to  a  cylinder  ana 
jointed  longitudinally  by  welded  butt  joints,  welded  by  a 
blow  pipe  using  acetylene  and  oxygen.  Tests  of  this  welded 
joint  by  R.  H.  Wyrill,  Waterworks  Engineer,  Swansea, 
showed  it  to  be  quite  as  strong  as  the  unwelded  steel  cut  from 
the  shell.  The  circumferential  joints  of  the  tube  were  made 
by  turning  up  the  edges  'of  the  sheets  and  welding  them ;  this 
gives  a  flexible  watertight  joint.  The  tube  was  made  in 
lengths  of  9  ft.  9^  ins.  and  its  ends  were  turned  up  all  around ; 
just  back  from  the  turned-up  ends  a  vertical  sheet  steel  collar 


Fig.  271. — Applying  External  Reinforcement  to  Bordenave  Pipe. 

was  welded  to  the  tube  to  form  a  strip  end  for  the  external 
coating.  These  details  are  shown  in  Fig.  270.  When  the  tube 
for  a  length  of  pipe  is  completed  the  inside  shell  reinforce- 
ment previously  made  is  slipped  into  it  and  the  outside  shell 
reinforcement  is  formed  on  it  as  a  mandril,  as  shown  by 
Fig.  271. 

Molding. — When  the  three  positions  of  the  steel  skeleton 
were  completed,  as  shown  by  Fig.  271,  they  were  set  on 
curved  wooden  curbs  made  to  the  exact  shape  necessary  to 
center  them  and  preserve  the  correct  thickness  of  cement 


586 


CONCRETE    CONSTRUCTION. 


coating.  A  collapsible  core  was  lowered  into  position  in  the 
inside,  and  a  two-part  sheet  steel  mold  was  erected  outside; 
the  space  between  core  and  mold  was  then  poured  with  a  thin 
mortar  of  one  part  Portland  cement  to  two  parts  clean  river 
sand.  During  the  process  of  pouring,  the  outer  steel  mold  is 
sharply  struck  with  wooden  mallets  to  facilitate  the  escape  of 
air  bubbles.  The  mortar  was  mixed  on  an  elevated  traveling 


Fig.  272. — Casting  Bordenave  Pipe  at  Swansea,  England. 

platform  which  is  shown  in  Fig.  272,  which  also  shows  a  com- 
pleted pipe,  a  core  being  withdrawn,  a  filled  mold  and  a  sec- 
tion of  reinforcement  set  up.  The  difficult  feature  of  the 
molding  process  was  found  to  be  the  determination  of  the 
time  for  withdrawing  the  core  and  removing  the  exterior 
mold ;  the  time  of  setting  of  the  mortar  was  different  in  warm 


AQUEDUCTS    AND    SEWERS.  587 

and  in  cool  weather  and  varied  with  the  wetness  of  the  mix- 
ture, the  brand  of  cement,  etc.  By  using  a  single  brand  of 
cement  that  ran  very  uniform  in  quality  and  time  of  setting 
it  was  possible,  however,  for  the  workmen,  after  a  little  prac- 
tice, to  gage  very  accurately  the  correct  time  for  removing 
the  molds.  With  four  sets  of  molds  a  gang  of  eight  men 
would  curb  16  pipes  per  day  under  favorable  conditions,  but 
when  the  temperature  was  low  it  was  not  possible  to  make 
more  than  six  or  eight  pipes.  The  pipes  were  allowed  to  stand 
four  or  five  days  after  the  removal  of  the  mold;  they  could 
then  be  removed  by  a  crane  and  laid  in  stock  until  used.  It 
was  found  advisable  to  let  the  pipes  age  about  four  weeksi 
before  laying;  by  this  time,  it  is  stated,  they  would  stand 
as  much  rough  usage  as  cast  iron  pipe. 

Laying. — The  pipes  were  laid  much  in  the  same  way  as 
cast-iron  pipes  are  laid ;  they  were  each  9  ft.  9^/2  ins.  long 
and  weighed  each  about  12  cwt.,  and  were  handled  by  ordinary 
tackle.  In  laying,  the  pipes  were  adjusted  end  to  end  and  the 
joint  enclosed  by  a  temporary  steel  ring  inside  which  the 
bitumen  seal,  Fig.  270,  was  run  and  allowed  to  set  when  the 
steel  ring  was  removed.  The  joint  was  then  encircled  by  a 
collar  of  similar  construction  to  the  pipe  itself  and  the  space 
between  collar  and  pipe  was  poured  with  cement  mortar. 
About  ten  lengths  of  pipe  were  laid  per  day  by  one  gang 
of  men,  one  jointer  and  his  assistant  making  all  the  cement 
and  bitumen  joints  as  fast  as  the  gang  could  lay  the  pipes. 


CHAPTER   XXIT. 

METHODS  AND  COST  OF  CONSTRUCTING  RESER- 
VOIRS AND  TANKS. 

• 

Floor,  wall  and  roof  work  of  structurally  very  simple  char- 
acter sum  up  the  task  of  the  constructor  in  reservoir  and 
tank  construction.  The  only  intricacy  involved  lies  in  form 
design  and  construction  for  cylindrical  tank  work.  Several 
examples  of  such  work  are  given  in  this  chapter,  and  in  each 
the  construction  and  handling  of  the  forms  are  described. 
To  repeat  details  here  would  serve  no  purpose,  but  one  gen- 
eral instruction  may  be  enunciated.  No  care  is  too  great 
which  ensures  rigidity  and  invariable  form,  both  in  the  con- 
struction of  the  individual  form  units  and  in  the  assembling 
of  these  units  into  the  complete  form.  This  is  particularly 
true  of  cylindrical  tank  work  and  especially  high  cylindrical 
tank  work  where  the  forms  are  moved  upward  as  the  work 
progresses.  To  the  designer  it  may  be  suggested  that  any 
beauty  he  may  gain  by  giving  the  walls  of  his  standpipe  a 
batter  is  paid  in  the  extra  cost  of  form  work. 

Concreting  in  tank  work  is  expensive.  The  reasons  are 
two.  The  work  has  to  be  done  in  a  narrow  space,  commonly 
pretty  well  filled  with  a  network  of  steel  rods  or  bars.  Again 
the  work  has  to  be  done  uniformly  well,  not  only  for  appear- 
ance sake  but  because  of  the  necessity  of  watertightness. 
Making  a  reservoir  watertight  is,  when  all  things  are  said,  the 
one  difficult  constructional  task  in  tank  work  and  the  con- 
tractor who  accepts  the  task  lightly  courts  trouble.  Excep- 
tionally good  concreting  is  essential  in  tank  work  if  water- 
tightness  is  to  be  secured. 

The  illustration  of  these  general  admonitions  will  be  found 
in  the  specific  examples  of  tank  and  reservoir  work  which 
follow. 


RESERVOIRS    AND    TANKS. 


589 


SMALL  COVERED  RESERVOIR.— The  reservoir  was 
designed  to  hold  75,000  gallons  of  water  for  fire  purposes.  As 
it  is  of  a  type  which  is  certain  to  be  frequently  constructed 
and  as  we  have  personal  knowledge  of  the  costs  recorded  we 
describe  the  work  in  some  detail.  The  specifications  stipu- 
lated that  the  reservoir  must  be  absolutely  watertight  and 
that  the  roof  should  be  capable  of  sustaining  a  load  of  300 
tons  evenly  distributed  and  a  live  load  of  5,000  Ibs.  on  two 


Fig.   273.— Sectional   Plan  of  75,000-Gallon  Reservoir. 

wheels.  Figure  273  shows  a  plan,  Fig.  274  a  longitudinal  sec- 
tion, Fig.  275  a  transverse  section  and  Fig.  276  the  column 
construction. 

Quantities  of  Work.— The  excavation  called  for  the  re- 
moval of  579  cu.  yds.  of  earth.  There  were  83  cu.  yds.  of 
concrete  in  the  structure,  although  the  plans  called  for  less, 
the  additional  amount  being  used  in  increasing  the  two  4-in. 
walls  to  6-in.  and  increasing  the  bottom  and  top,  on  one  end, 


590 


CONCRETE    CONSTRUCTION. 


so  as  to  give  perfect  drainage.     The  yardage  was  divided  as 
follows : 

Cu.  yds. 

Footings 3.5 

Columns ..«.'... 6.8 

Sides , 22.6 

Girders    „  . .  « 1 1  .o 

Top    ' 20.0 

Floor    19.1 


Total    83.0 


*%&&>&**  - 


yyj 

T^r^fe- 


Enq-Corfr       Q-frtfrSPBaB  'lQ-frt£WQ'Bars.fc'CtoC 

Fig.  274. — Longitudinal  Section  of  75,000-Gallon  Reservoir. 

A  manhole  had  to  be  put  in  the  top  and  a  sump  in  the 
bottom.  Several  pipes  also  had  to  be  placed  in  the  concrete. 
None  of  these  details  is  shown  on  the  plan.  The  structure 
had  to  be  waterproofed. 

Excavation. — The  excavation  was  made  with  pick  and 
shovel  and  the  material  hauled  away  in  carts,  the  distance  to 
the  dump  being  700  ft.  The  top  was  shoveled  directly  into 
the  carts,  while  the  rest  was  handled  two  and  three  times. 
When  the  reservoir  was  finished  dirt  had  to  be  filled  in  around 
the  sides  and  puddled. 

Wages. — The  following  rates  of  wages  were  paid  on  the 
job: 

Foreman    $3-OO 

Carpenter    3.50 

Carts   and    driver    , 3.50 

Laborers    1.50 


RESERVOIRS    AND    TANKS. 


591 


The  carpenters  worked  8  hours  a  day  and  were  paid  time 
and  a  half  for  overtime.  The  rest  worked  ten  hours  per  day 
and  were  paid  regular  rates  for  overtime. 


Fig.  275. — Transverse  Section  of  75,000-Gallon  Reservoir. 

Forms. — Carpenters  framed  and  erected  the  forms,  but  la- 
borers did  all  the  carrying  for  them.  Laborers  also  tore  down 
the  forms.  For  the  girders  and  columns  2-in.  boards  were 
used,  but  for  the  sides  i-in.  boards  with  3x4-in.  scantlings 


Erfy-Contr 


4f 

'5=^ 

V 

X 

*~/f  '  ;/ 

1 

S 

\ 

*4 

x1 

^ 

«--2'3—  ^ 

Fig.  276.— Column  Construction  for  75,000-Gallon  Reservoir. 

were  used.  The  props  for  supporting  the  girder  and  top 
forms  were  3x4.  Except  for  columns  and  girders  and  some 
props,  all  the  forming  was  used  three  times.  The  lumber 
cost: 


592  CONCRETE    CONSTRUCTION. 

400  ft.  B.  M.  at  $24 $  9.60 

S,ooo  ft.  B.  M.  at  $18 144.00 

Total    $153.60 

This  makes  an  average  price  per  1,000  ft.  of  about  $18.30, 
which  price  we  shall  use  in  giving  costs. 

The  cost  of  framing  and  erecting  the  forms  was  $167.27  for 
the  sides,  columns,  girders  and  top.  In  the  forms  for  the 
sides,  forming  was  only  used  on  one  side  of  the  concrete  for 
two  sides,  the  earth  bank  being  used  for  the  other  side  of  the 
forms,  but  on  the  other  two  sides  the  banks  had  caved  in, 
and  forming  was  used  on  both  sides  of  the  wall.  The  cost 
per  cubic  yard  for  forms  was : 

Lumber $2.54 

Framing  and  erecting 2.77 

Tearing   down .54 


Total $5.85 

This  cost  is  for  the  yardage  of  60.4  on  which  forms  were 
actually  used.  For  the  total  yardage  in  the  tank  the  cost  was : 

Lumber    $1.85 

Framing  and   erecting   2.01 

Tearing  down    .40 

Total    $4.26 

The  common  labor  cost  of  assisting  to  erect  the  forms  was 
15  per  cent  of  the  total.  Nothing  is  allowed  for  foreman,  for 
the  contractor  acted  as  his  own  foreman. 

The  cost  of  forms  per  1,000  ft.  for  the  amount  of  lumber 
purchased  was: 

Lumber    $18.30 

Framing  and  erecting   19.90 

Tearing  down    4.00 


Total    $42.20 

As  the  lumber  was  used  three  times,  the  cost  per  thousand 
for  all  work  and  materials  on  the  forms  would  be  just  one- 
third  of  this — namely:  $14.06. 


RESERVOIRS    AND    TANKS.  593 

Since  the  framing,  erecting  and  tearing  down  cost  $19.90 
plus  $4,  or  $23.90  per  M.  ft.  B.  M.  purchased,  and  since  the 
lumber  was  used  three  times,  the  labor  cost  nearly  $8  per  M. 
each  time  that  the  lumber  was  used.  It  will  be  noted  that 
8,400  ft.  B.  M.  were  required  for  the  83  cu.  yds.  of  concrete, 
or  a  trifle  more  than  100  ft.  B.  M.  per  cubic  yard. 

It  will  be  of  interest  to  see  the  labor  costs  of  forms  for 
the  various  parts  of  the  structure. 

For  the  sides  the  cost  of  framing  and  erecting  the  forms 
was  $4.19  per  cubic  yard.  Of  this  cost  4  per  cent,  was  for 
common  labor  and  the  rest  for  carpenters.  The  tearing  down 
cost  47  cts.  per  cubic  yard.  For  the  columns  the  erecting  was 
$2.35,  of  which  I  per  cent  was  for  common  labor.  The  tearing 
down  cost  47  cts.  For  the  girders  and  top  the  erecting  cost 
$1.83,  of  which  35  per  cent,  was  common  labor.  The  tearing 
down  cost  61  cts.  per  cubic  yard.  A  summary  would  show : 

Girders 

Sides         Columns        and 
per  per  top  per 

cu.  yd.         cu.  yd.         cu.  yd. 

Framing   and    erecting    $4-19  $2-35  $1-83 

Tearing   down    47  47  -&l 


Total    $4-66  $2.82  $2.44 

The  greater  cost  of  the  columns  forms  over  the  girders  and 
top  was  due  to  the  fact  that  the  columns  forms  were  handled 
almost  exclusively  by  the  carpenters,  and  also  in  setting  them 
great  care  and  much  time  had  to  be  used  to  get  them  plumb 
and  in  line.  The  cost  of  the  forms  for  the  sides  was  about 
twice  as  great  as  that  for  the  top  and  girders.  The  reasons 
for  this  are  evident.  The  walls  had  forms  on  both  sides,  while 
the  top  needed  forming  only  underneath  it,  the  area  covered 
on  the  forms  being  about  2,200  sq.  ft.  as  compared  to  1,000 
sq.  ft.  The  side  forms  had  to  be  set  plumb  and  kept  so.  The 
framing  was  done  ahead,  but  nearly  half  of  the  lumber  in  the 
sides  was  erected  as  the  concrete  was  being  put  in  place. 
The  forms  for  the  top  were  all  put  in  place  before  any  con- 
creting -was  done  on  the  top,  and  the  carpenters  discharged. 
A  much  larger  per  cent,  of  common  labor  could  be  used  in 
placing  forms  for  top  and  girders  than  on  the  sides.  The 


594  CONCRETE    CONSTRUCTION. 

props  were  nearly  all  put  in  place  by  laborers.  The  extra 
cost  of  tearing  down  the  forms  for  the  top  was  due  to  the 
fact  that  the  lumber  all  had  to  be  handled  one  piece  at  a 
time  through  a  small  manhole  in  the  top,  and  carried  about 
150  ft.  to  be  piled. 

To  all  the  costs  for  forming  should  be  added  6  cts.  per  cubic 
yard  for  nails,  wire  and  lines  used  on  the  forms. 

Concrete. — The  mixtures  varied  for  the  different  members. 
The  cost  of  materials  was  as  follows : 

Cement,   no  bbls.  @  $1.12 $123.20 

24-in.  stone,  80  cu.  yds.,  @  $1.86 148.80 

Gravel,  3  cu.  yds.,  @  $1.33 4.00 

Sand,  42  cu.  yds.,  @  $1.20 50.40 

The  sides  were  first  put  in  place,  then  the  center  columns 
were  built,  following  which  the  bottom  was  placed.  Then  the 
forms  were  erected  for  the  top  and  the  girders,  and  these  cast. 
In  building  the  sides,  one  side  and  half  of  the  two  ends  were 
built  at  one  time,  and  then  forms  erected  for  the  other  half 
of  the  sides.  For  the  sides  the  mixing  was  done  in  the  bottom 
of  the  reservoir.  For  the  rest  of  the  structure  it  was  done  on 
the  ground,  the  mixing  board  being  along  side  of  the  reser- 
voir. The  labor  cost  of  the  concrete  work  for  the  various 
members  and  the  average  per  cubic  yard  was  as  follows : 

Col- 
umns and 

Foot-  Bot-  Gird-  Av- 

Sides.       ings.  torn.  ers.  Top.  erage. 

Cubic    yards    22.6           10.3  19.1  11  20.0  83. 

Preparing  and  cleaning  up.. $0.166       $0.060        $0.095       $0.065 

Handling   materials    1.022            .306  $0.070  .198  $0.187  .404 

Cleaning    out    forms 040            .070  .053  .032 

Mixing    and    placing 1.542            .728  .353  .792  1.080  .952 

Ramming     1.090           .540  .455  .450  .597  .673 

Handling    steel    890           .020  395  .083  .324 


Total     $4.750       $1.654        $0.878        $2.000       $2.000       $2.450 

The  total  cost  of  labor  was  $203.35.  The  mixing  was  done 
entirely  by  hand.  Some  plastering  was  done  to  the  walls 
after  the  forms  were  taken  off,  and  the  sides  and  bottom  were 
washed  with  a  brush  with  cement  and  water.  The  plastering 
cost  $6.60,  including  a  barrel  of  cement  and  the  washing  or 
grouting,  two  coats,  cost  $9.10,  including  a  barrel  of  ce- 
ment. This  added  a  cost  of  19  cts.  per  cubic  yard  to  the  con- 
crete work,  making  the  total  cost  per  cubic  yard  $2.65. 

It   was   a   mistake   to   have   mixed   the   concrete   for  the 
sides  in  the  bottom  of  the  reservoir,  as  it  made  two  handlings 


RESERVOIRS    AND    TANKS. 


595 


of  the  materials  and  compelled  all  the  concrete  to  be  raised  by 
hand  to  place  it  in  the  forms.  This  accounts  for  the  high 
cost  of  these  two  items. 

The  handling  of  the  steel  was  high  for  the  side  walls,  as  it 
was  all  separated  and  put  into  piles  for  the  different  panels 
and  members  in  getting  it  out  of  the  pile  for  the  sides.  The 
rammers  not  only  rammed  the  concrete  but  they  also  bent 
down  the  prongs  of  the  steel  to  get  them  in  place  in  the  nar- 
row forms,  and  afterwards  had  to  pull  out  these  prongs.  This 
had  to  be  done  for  every  piece  of  steel  used,  and  readily 
doubled  the  cost  of  ramming.  The  high  cost  of  ramming  the 
top  was  caused  by  the  fact  that  the  6  ins.  of  concrete  had  to 
be  placed  in  three  layers  and  each  rammed.  The  steel  handling 
was  high  on  account  of  the  prongs  entangling  the  pieces 
with  others,  making  them  hard  to  handle.  The  cost  of 
handling  steel  per  ton  was  about  $4,  or  0.2  ct.  per  pound.  The 
steel  was  all  handled  by  common  laborers. 

The  stock  piles  of  material  had  to  be  made  along  a  street 
and  alley  and  thus  caused  the  material  to  be  handled  in  wheel- 
barrow several  hundred  feet. 

The  preparing  to  mix  concrete,  the  cleaning  up  afterwards 
and  the  cleaning  out  of  forms  are  items  that  are  seldom  kept 
separate  from  the  others. 

The  cost  of  mixing  and  placing  is  high,  owing  to  the  fact 
that  working  space  was  small  and  the  mixers  had  to  wait  un- 
til the  concrete  was  taken  off  the  board  and  placed  in  the 
forms  before  starting  another  batch.  This  also  meant  an  in- 
creased cost  in  the  ramming,  as  the  rammers  were  idle  some 
time  waiting  for  a  new  batch  to  be  mixed. 

The  total  cost  of  concrete,  including  labor  and  materials, 

per  cubic  yard  on  a  basis  of  the  83  cu.  yds.  was : 

Per  cu.  yd. 

Cement,    i  1-3   bbls.,   @   $1.12 $  i-49 

Stone,  i  cu.  yd I -86 

Sand   l/2   cu.  yd 

Steel    

Forms,  100  ft.  B.  M.,  @  $18.30 

Labor  on  forms 

Labor  on  concrete  and  steel    

Total  $15-62 


596  CONCRETE    CONSTRUCTION, 

The  cost  of  a  foreman  is  not  included  in  this,  as  the  con- 
tractor looked  after  the  men  himself. 

Waterproofing. — The  waterproofing  of  the  structure  proved 
a  serious  problem.  It  was  thought  at  first  that  the  concrete 
itself  would  be  nearly  water  tight,  but  the  tank  leaked  like  a 
sieve.  After  considering  several  methods,  an  agent  of  a 
European  waterproofing  mixture  prevailed  upon  those  inter- 
ested to  try  his  compound.  To  apply  it,  the  walls  had*  to  be 
dry,  so  a  large  coal  burning  stove  was  put  in  the  reservoir 
and  a  fire  kept  up  day  and  night.  While  this  drying  process 
was  going  on  several  light  falls  of  snow  occurred,  and  this 
had  to  be  cleared  away  to  make  the  walls  and  roof  dry.  Two 
coats  of  the  mixture  were  applied  according  to  the  agent's  in- 
structions, and  the  reservoir  was  tested.  The  water  fell 
nearly  half  a  foot  in  an  hour's  time. 

Then  a  waterproofing  contractor  agreed  to  make  the  res- 
ervoir water  tight  with  paper  and  tar,  by  applying  it  on  the 
inside.  Three  thicknesses  of  paper  were  laid  on  the  bottom 
and  run  well  up  on  the  sides,  each  layer  of  paper  being  well 
covered  with  a  preparation  of  tar.  Upon  testing  it,  it  was 
found  that  the  leaking  had  been  reduced  about  50  per  cent. 
A  preparation  of  asphalt  was  then  placed  over  this,  but  upon 
a  third  test  the  tank  still  leaked.  As  the  sub-contractor  had 
verbally  agreed  to  make  it  water  tight  for  $125,  only  this 
amount  was  paid  him.  After  this  last  test  he  refused  to  do 
any  more  work. 

After  these  attempts  the  sides  of  the  reservoir  were  exposed 
on  the  outside  by  excavating  around  it,  and  a  one-brick-wall 
built  up  a  few  inches  from  the  concrete.  This  space  was  filled 
in  with  rich  cement  mortar  and  the  ground  once  more  filled 
in  around  the  structure.  This  work  and  the  materials  used 
in  it  cost  $1,240.  Upon  a  fourth  test  the  reservoir  was  found 
to  be  water  tight.  Thus  more  than  a  third  of  the  cost  of  the 
entire  work  was  in  waterproofing  the  structure,  and  this  made 
the  contract  a  money  losing  one,  as  this  heavy  cost  was  not 
anticipated. 

Several  items  of  miscellaneous  work  are  listed  in  the  total 
cost  of  the  reservoir,  such  as  filling  in  and  puddling  around 
reservoir  and  replacing  cobble  paving.  The  top  of  the  struc« 


RESERVOIRS   AND    TANKS.  597 

ture  was  used  as  a  bin  for  the  storage  of  coal.  For  this  pur- 
pose eight  I-beams  were  embedded  in  concrete  around  the 
top  to  be  used  as  posts  for  the  sides  of  the  bin.  The  cost  of 
placing  these  is  given. 

Total  Cost. — The  cost  of  the  structure  without  any  profits  was : 

579  cu-  yds.  excavation  @  $.896 $    529.65 

Steel    395.00 

Crushed    stone    148.80 

Gravel    4>oo 

Sand    50.40 

Cement 123.20 

Lumber    153.60 

Labor  on  forms 200.09 

Labor  on  concrete  203.35 

Plastering 5.60 

Sides  and  bottom  9.10 

Nails,  wire,  etc 4.98 

Bailing  water    21.19 

Building   temporary   fence    1.65 

Extra  excavation  for  forms,  footings,  etc.  13-9O 

Setting  I-beams  in  concrete 17&5 

Filling  in  and  pudding  around  reservoir 3447 

Replacing  cobble  paving   4.30 

Hauling  tools 3.60 

Heating  reservoir  and  handling  snow I4-5O 

Waterproof  mixture    29.00 

Labor  applying  it    9.74 

Applying  paper  and   tar,  labor  and   materials 125.00 

Labor  and  materials  of  final  waterproofing 1,240.00 

Tools    48.75 

General    expense    210.00 


Total $3.602.52 

COVERED  RESERVOIR,  AT  FORT  MEADE,  SOUTH 
DAKOTA.  —  The  following  account  of  the  method 
and  cost  of  constructing  a  5oo,ooo-gallon  reservoir  is  com- 
piled from  information  furnished  by  Mr.  Samuel  H.  Lea,  M. 
Am.  Soc.  C.  E.  As  shown  by  Fig.  277,  the  reservoir  consists 
of  two  equal  compartments,  each  50  x  60  ft.  inside  dimensions, 


598 


CONCRETE    CONSTRUCTION. 


with  rounded  corners.     Both  compartments  are  covered  with 
a  3-in.  slab  roof  carried  on  the  walls  and  interior  columns. 

The  concrete  was  a  1-2-4  Portland  cement,  sand  and  broken 
stone  mixture,  mixed  by  hand  on  a  movable  platform.  A  con- 
crete gang  consisted  of  four  men  who  were  each  paid  $2.75 
per  day.  They  wheeled  the  materials  from  the  supply  piles  to 
the  mixing  platform,  mixed  the  concrete  and  deposited  it  in 
place.  During  the  construction  of  the  footings  and  floor  two 
concrete  gangs  were  employed,  but  after  the  walls  were 
started,  one  gang  only  was  required  for  concrete  work ;  the 
other  gang  was  then  put  to  work  assisting  the  carpenters. 

c 
'1 


Z2^ 

Section         A-B. 
Fig.   277.— Reservoir  at  Ft.  Meade,   S.   D. 

The  sand  and  stone  were  wheeled  to  the  platform  in  iron 
wheelbarrows  of  2^/2  cu.  ft.  capacity.  The  cement  was  in  >^- 
bbl.  sacks  and  each  sack  was  taken  as  I  cu.  ft.  Each  batch 
of  concrete  contained  the  following  quantity  of  material: 

2Y-2   sacks  of  cement    2^  cu.  ft. 

2  wheelbarrows    of   sand    5 cu-  ft- 

4  wheelbarrows  of  stone    io"cu.  ft. 

The  quantities  of  sand  and  stone  were  adjusted  so  as  to 
form  the  proper  proportion  for  making  a  dense  concrete. 


RESERVOIRS    AND    TANKS. 


599 


From  time  to  time,  as  the  work  progressed,  experiments  were 
made  to  determine  the  percentage  of  voids  both  in  the  sand 
and  the  crushed  stone ;  and,  in  this  way,  uniformity  in  com- 
position was  secured.  The  mixture  was  made  quite  wet  in 
order  to  insure  a  free  flow  around  the  reinforcing  bars.  On 
account  of  the  narrow  space  inside  the  forms  and  the  num- 
ber of  reinforcing  bars  therein  care  was  taken  to  cause  the 
mixture  to  be  well  distributed  throughout.  The  wet  concrete 
was  well  spaded  in  an  effort  to  secure  a  smooth  surface  next 
to  the  forms.  This  was  generally  accomplished,  but  some 
rough  places  which  showed  after  the  removal  of  the  forms 
required  patching  up. 

In  constructing  the  footings  some  concrete  was  first  de- 
posited in  place  and  the  metal  reinforcement  was  embedded 
therein.  For  the  floor  reinforcement  the  lower  bars  were 
carefully  embedded  in  the  concrete  after  it  had  been  brought 
to  a  suitable  height;  the  upper  bars  were  then  placed  cross- 
wise upon  the  lower  ones  and  kept  in  position  until  the  re- 
mainder of  the  concrete  had  been  deposited  around  and  over 
them.  In  the  wall  footings  a  depression  or  groove,  several 
inches  deep,  was  left  under  the  wall  space  for  its  entire  length. 
This  ensured  a  good  bond  between  the  wall  proper  and  the 
footing. 

The  concrete  floor  in  each  compartment  was  built  in  one 
continuous  operation,  the  object  being  to  secure  a  practically 
monolithic  construction.  The  lower  reinforcing  bars  in  the 
floor  were  embedded  at  the  proper  depth  in  the  fresh  concrete 
and  the  upper  bars  were  then  placed  crosswise  upon  the 
lower  ones;  the  two  sets  were  then  wired  together  at  a 
sufficient  number  of  places  to  prevent  displacement  while  the 
remaining  concrete  was  being  deposited  around  and  over  them. 

The  reinforcement  for  the  walls  and  columns  was  erected 
in  place  upon  the  footings  and  formed  a  steel  skeleton  around 
which  the  forms  were  erected.  The  upright  bars  in  the  walls 
were  held  together  and  at  the  proper  distance  apart  by  means 
of  templates  consisting  of  wooden  strips  in  which  holes  were 
bored  at  suitable  intervals  to  receive  the  bars.  The  templates 
were  maintained  in  a  horizontal  position  and  were  moved 
upward  as  the  concrete  advanced  in  height.  The  horizontal 


6oo  CONCRETE    CONSTRUCTION. 

reinforcing  bars  were  wired  in  place  to  the  upright  bars ;  they 
were  placed  in  position  ahead  of  the  concreting  as  the  wall 
was  built  up. 

The  corrugated  bars  in  beam  and  girders  were  placed  in 
position  in  the  forms  and  held  up  by  blocks  which  were  re- 
moved as  the  forms  were  filled  with  concrete.  The  expanded 
metal  reinforcement  for  the  roof  slab  was  placed  so  as  to  be 
close  to  the,  lower  face  of  the  slab,  but  far  enough  up  to  be 
entirely  enveloped  in  the  concrete. 

The  wall  forms  were  made  of  2-in.  planks,  surfaced  on 
the  inner  side  and  placed  horizontally  on  edge.  They  were 
held  in  place  by  4  x  4-in.  posts  spaced  at  intervals  of  about 
4  ft.,  in  pairs  on  opposite  sides  of  the  wall.  The  posts  were 
firmly  braced  on  the  outside ;  they  were  prevented  from 
spreading  by  connecting  wires  passing  through  the  wall  space 
between  the  edges  of  adjacent  planks.  At  the  rounded  cor- 
ners of  the  reservoir  the  pairs  of  posts  were  spaced  about  two 
feet  apart  and  the  curve  was  made  by  springing  thin  boards 
into  place  to  fit  the  curve  and  nailing  them  to  the  posts.  The 
posts  were  high  enough  to  reach  to  the  top  of  the  wall;  the 
siding  was  built  up  one  plank  at  a  time  as  the  concrete  work 
progressed.  Column  forms  were  made  of  2-in.  planks  on 
end,  extending  from  floor  to  girder.  Three  sides  were  en- 
closed and  one  side  was  left  open  to  receive  the  concrete ;  this 
side  was  closed  up  as  the  concreting  advanced  in  height. 

The  beam  and  girder  forms  were  open  troughs  of  the  re- 
quired dimensions,  made  of  2-in.  plank,  surfaced  on  inner 
faces.  The  form  of  centering  for  the  roof  slab  consisted  of  a 
smooth,  tight  floor  of  2-in.  planks,  extending  between  the 
open  tops  of  column,  beam  and  girder  forms  over  the  entire 
area  between  enclosing  walls  of  the  reservoir.  The  centering 
and  the  beam  and  girder  forms  were  supported  by  6  x  6-in. 
posts  resting  upon  the  floor  below. 

The  regular  carpenter  gang  consisted  of  a  foreman  car- 
penter at  $5  per  day,  a  carpenter  at  $3.50  per  day,  and  two 
helpers  at  $2.75  per  day.  During  the  early  concrete  work  of 
making  footings  and  floor,  where  forms  were  not  required,  the 
carpenter  force  was  employed  in  erecting  the  steel  skeleton 
for  the  walls.  The  upright  bars  were  placed  in  position  and 
secured  by  temporary  wooden  stays  extending  from  the  up- 


RESERVOIRS    AND    TANKS.  6oi 

per  portion  of  bars  to  the  surface  of  ground  outside  of  ex- 
cavation. These  stays  were  removed  after  concreting  had 
advanced  to  a  sufficient  height  to  hold  the  steel  securely  in 
place. 

The  wages  paid  the  concrete  gang  which  mixed  and  placed 
all  the  concrete  and  the  carpenter  gang  which  constructed 
and  erected  the  forms  and  placed  the  reinforcement  have  been 
given  above.  The  costs  of  construction  materials  on  the  site 
were : 

Cement,  per  barrel   $2-57 

Sand,  per  cu.  yd 1.80 

Stone,  per  cu.  yd 3.15 

Lumber,  per  M.  ft.  B.  M 27.50 

The  quantities  in  the  completed  concrete  structure  were  as 
follows : 

Total  volume  of  concrete  in  reservoir 704.71  cu.  yds. 

Total  volume  of  steel  reinforcement  in  reservoir.  5.57  cu.  yds. 


Total  volume  of  material  in  completed  structure. 710.28  cu.  yds. 

The  steel  was,  therefore,  about  0.8%. 
Volume   of   material    in    structure    exclusive    of 

roof  slab    648.35  cu.  yds. 

Volume  of  material  in  roof  slab 61.93  cu.  yds. 

Total  710.28  cu.  yds. 

The  cost  of  the  structure  per  cubic  yard  of  concrete,  ex- 
clusive of  the  roof  slab,  was  as  follows: 

Item.  Per  cu.  yd. 

Crushed  stone  $3.168 

Sand 842 

Cement  3-^59 

Reinforcement  4-959 

Labor,  mixing  and  placing  concrete  i-721 

Forms,  labor  and  material  2.960 

Total    $17.509 

In  constructing  the  roof  slab  the  expanded  metal  reinforce- 
ment raised  the  unit  cost.  For  this  portion  of  the  work  the 
costs  were : 


602  CONCRETE    CONSTRUCTION. 

Item.  Per  cu.  yd. 

Expanded  metal  reinforcement  $  5.241 

Other  items,  same  as  above   I2-55O 


Total    $17.791 

The  floor  and  the  inside  surface  of  reservoir  walls  were 
covered  with  a  coating  of  cement  mortar  composed  of  one 
part  Portland  cement  and  one  part  sand.  The  wall  plaster- 
ing was  from  y2  in.  to  ^4  m-  thick;  it  was  applied  in  two  coats. 
The  floor  finish  was  laid  in  alternate  strips  about  i  in.  thick 
and  3  ft.  wide.  After  the  strips  first  laid  had  hardened  the 
remaining  strips  were  laid,  the  edges  being  grouted  to  ensure 
tight  joints. 

The  outside  of  walls  and  roof  was  covered  with  a  coating 
of  tar  which  was  heated  in  an  open  kettle  to  a  temperature 
of  about  360°  F.  and  then  applied  with  a  brush  or  mop. 

The  cost  of  wall  and  floor  plastering  was  44.4  cts.  per 
square  yard,  itemized  as  follows : 

Cement    26.4  tts. 

Sand    2.6  cts. 

Labor    1 5.4  cts. 

Total 44.4  cts. 

The  cost  of  outside  waterproofing  was  4  cts.  per  square 
yard,  distributed  as  follows : 

Material 2.5  cts. 

Labor    1.5  cts 

Total    4.0  cts. 

While  some  of  the  cost  items  are  apparently  high  when 
compared  with  the  cost  of  similar  work  in  other  places,  it 
should  be  remembered  that  the  isolated  locality  and  the  local 
conditions  were  unfavorable  for  low  cost.  Owing  to  the  iso- 
lated location  of  the  reservoir  with  respect  to  large  markets 
and  also  to  local  sources  of  supply  the  cost  of  material  and 
labor  was  quite  high.  All  construction  material,  except  some 
of  the  stone  for  crushing,  had  to  be  hauled  over  a  mountain 
road  from  3  to  4  miles  to  the  top  of  the  hill  selected  for  the 
reservoir  site.  Labor  was  scarce  and  commanded  a  wage  of 


RESERVOIRS    AND    TANKS. 


603 


$2.50  per  day  for  ordinary  work ;  the  laborers  mixing  concrete 
were  paid  $2.75  per  day.  Another  source  of  much  relative  ex- 
pense was  the  high  cost  of  lumber  and  carpenter  work  on 
the  forms.  On  account  of  the  thinness  of  the  walls  and  roof, 
the  cost  of  lumber  and  labor  required  per  cubic  yard  of  con- 
crete was  considerable.  A  part  of  the  lumber  was  used  the 
second  time  in  forms,  but  it  was  found  impracticable  to  delay 
the  work  by  waiting  for  the  concrete  to  harden  before  begin- 
ning the  new  portions  of  the  walls.  This  lumber  was  sold 


Fig.-  278. — Reservoir  Forms,    Bloomington,   111. 

after  the  completion  of  the  work,  but  the  salvage  was  incon- 
siderable, amounting  to  less  than  10  per  cent,  of  the  original 
cost. 

CIRCULAR  RESERVOIR,  BLOOMINGTON,  ILL.— An 

open  circular  reinforced  concrete  reservoir  was  constructed 
in  1905-6  for  the  water-works  of  Bloomington,  111.  This  res- 
ervoir is  300  ft.  in  diameter,  15  ft.  deep  at  the  circular  wall 
and  25  ft.  deep  at  the  center  of  the  spherical  bottom.  The 
wall  construction  is  shown  clearly  by  Fig.  278,  and  the  floor 
is  a  6-in.  spherical  slab  reinforced  by  a  mat  of  %-m.  round 


604  CONCRETE    CONSTRUCTION. 

robs  placed  6  ins.  on  centers  in  both  directions.  The  wall 
reinforcement  is  corrugated  bars.  Neither  the  wall  nor  the 
bottom  has  expansion  joints. 

Concrete. — The  specifications  required  not  less  than  I  part 
Portland  cement  to  2  parts  sand  and  5  parts  clean  gravel,  and 
stipulated  that  there  should  always  be  more  than  enough 
cement  to  fill  the  voids  in  the  sand  more  than  enough  mortar 
to  fill  the  voids  in  the  gravel.  The  proportions  were  varied, 
depending  on  the  character  of  the  available  material  and  on 
the  location  the  concrete  was  to  occupy.  The  stipulations  re- 
garding the  minimum  quantities  of  cement  and  mortar  were, 
however,  always  at  least  fulfilled.  A  1-3-4  mixture  of  cement, 
broken  stone  and  gravel  was  largely  used  in  the  footing  and 
wall.  The  grr.vel  was  fine  and  contained  40  to  50%  of  sand ; 
the  broken  stone  was  the  crusher-run,  with  the  dust  screened 
out,  and  the  maximum-sized  pieces  not  larger  than  those 
vyhich  would  pass  a  2-in.  screen.  The  mortar  facing  on  the 
frcnt  face  of  the  wall  was  made  of  i  part  cement  to  4  parts 
fine  gravel,  containing  sand.  Some  gravel  from  the  excavation 
was  used  in  the  concrete  for  the  floor.  This  gravel  was  so 
fine  that  about  one-quarter  of  it  was  replaced  with  broken 
stone  and  the  mixture  made  1-6.  Both  faces  of  the  wall  were 
painted  with  a  i-i  mixture  of  cement  and  sand;  the  inner 
face  was  also  painted  with  a  i-i  mixture  of  waterproof  Star 
Stettin  Portland  cement  and  sand.  The  sidewalk  finish  on 
the  surface  of  the  floor  consisted  of  1-1^2  mortar. 

Mixing  and  Handling. — The  concrete  mixing  plant  was  set 
up  outside  of  the  site  of  the  reservoir  along  a  side  track  from 
the  railroad.  The  concrete  materials  were  delivered  on  the 
side  track,  except  some  gravel  from  the  excavation  that  was 
used.  A  Foote  portable  continuous  mixer  was  used  in  making 
the  concrete  for  the  wall  footings  and  the  wall.  It  was 
mounted  so  it  could  discharge  into  dump  cars  on  a  service 
track  laid  on  the  ground.  A  double  hopper  was  built  up  over 
the  mixer,  one  compartment  for  sand  and  one  for  broken 
stone.  The  end  of  a  service  track  leading  from  the  side  track 
was  laid  on  an  inclined  trestle  up  to  a  floor  level  with  the 
top  of  this  double  hopper,  the  materials  being  hauled  in  dump 
cars  from  the  side  track  to  the  hopper.  The  service  track 
from  the  mixer  extended  entirely  around  the  wall,  and  10  ft. 


RESERVOIRS  ,  AMD    TANKS.  .  605 

from  it,  on  the  embankment  made  there  with  earth  from  the 
trench  for  the  wall-footing.  The  concrete  was  dumped  from 
the  cars  on  the  service  track  to  portable  shoveling  platforms 
near  the  point  where  work  on  the  wall  was  in  progress.  It  was 
shoveled  by  hand  from  these  platforms  to  place  in  the  forms 
as  the  presence  of  the  reinforcement  bars  in  the  narrow  forms 
precluded  dumping  in  large  quantities.  The  footing  was  built 
without  forms  up  to  the  right-angle  joint  between  it  and  the 
base  of  the  wall  at  the  front,  and  to  the  top  of  the  45°  slope 
on  its  rear  face.  A  layer  of  concrete  2.5  in.  thick  was  first 
placed  in  the  completed  trench.  The  reinforcement  bars  near 
the  bottom  were  then  laid  on  this  green  concrete,  the  vertical 
bars  near  the  front  face  of  the  wall  usually  being  erected  at 
the  same  time.  The  concrete  in  the  toe  of  the  footing  and  in 
the  footing  proper  up  to  the  top  layer  of  reinforcement  was 
then  laid.  After  the  top  layer  of  reinforcing  bars  had  been 
laid,  the  footing  was  completed,  except  for  a  top  layer  about 
2  ins.  thick  at  the  base  of  the  front  face  of  the  wall  and  i$ 
ins.  thick  at  the  toe  of  the  footing.  This  left  a  strip  of  sur- 
face about  6  ft.  wide,  sloping  at  about  i  in  6  from  the  wall 
toward  the  center  of  the  reservoir,  and  furnished  the  widest 
and  best  possible  bond  for  the  joint  which  had  to  be  made 
when  floor  was  laid. 

Location  and  Construction  of  Forms  and  Wall. — The  de- 
sign of  the  wall  of  the  reservoir,  although  simple  in  itself,  re- 
quired unusually  accurate  work  in  the  location  and  construc- 
tion of  the  forms  for  it.  The  location  was  made  with  very 
little  difficulty,  however,  by  an  arrangement  devised  by  the 
contractor  which  enabled  the  foreman,  without  the  aid  of  an 
engineer,  to  set  the  necessary  grade  and  reference  stakes.  A 
post,  10  ins.  in  diameter,  was  set  very  accurately  and  firmly 
in  the  ground  at  the  center  of  the  reservoir.  This  post  was 
sawed  off  squarely  on  top  so  that  the  line  of  collimation  of  an 
engineer's  transit  set  on  it  without  a  tripod  would  be  exactly 
at  the  grade  of  the  top  of  the  completed  wall  of  the  reservoir. 
A  200-ft.  steel  tape  was  used  to  measure  the  radial  distance 
from  a  nail  in  the  center,  post  to  the  posts  of  the  back,  or  out- 
side forms  for  the  wall.  In  the  form  for  the  back  face  of  the 
wall  2x6-in.  posts,  spaced  one  one-hundredth  of  the  circum- 
ference apart,  were  set  considerably  in  advance  of  any  con- 


6o6  CONCRETE    CONSTRUCTION. 

« 

crete  work,  and  were  made  the  basis  of  all  measurement  in 
building  the  forms.  The  forms  as  originally  planned  are 
shown  in  Fig.  278. 

The  wall,  when  started,  was  built  continuously  in  both  di- 
rections from  the  starting  point.  The  back  forms  consisted 
of  planks  for  lagging  nailed  to  vertical  posts,  which  were  ac- 
curately set  and  firmly  braced.  The  front  forms  were  made 
in  lengths  equal  to  one  one-hundredth  of  the  circumference 
of  the  reservoir,  and  when  set  up  were  fastend  to  the  back 
forms.  Twenty-one  of  these  front  form  sections  were  built 
and  all  set  up  at  once.  Concrete  was  filled  in  between  the 
front  and  back  forms,  starting  at  the  central  form,  and  was 
rammed  in  inclined  layers,  sloping,  at  about  I  on  6,  both  ways 
towards  the  end  forms.  This  method  was  adopted  in  order 
that  the  concrete  might  be  laid  continuously  and  without 
joints.  The  lagging  of  i-in.  boards  on  the  vertical  portion 
of  the  sections  was  nailed  to  the  vertical  posts,  and  was  car- 
ried up  just  ahead  of  the  concrete  filling. 

When  the  concrete  had  reached  the  top  of  the  central  one 
of  the  21  sections  of  the  forms,  and  the  concrete  in  that 
section  had  set  sufficiently,  the  section  was  broken  up  and 
removed,  leaving  two  sets  of  10  sections  of  the  forms.  Sub- 
sequently the  other  forms  could  be  removed  in  turn  as  desired 
without  being  broken  up.  As  the  filling-in  proceeded  between 
the  two  sets  of  10  forms  each,  the  form  in  each  set  nearest  the 
starting  point  was  removed,  carried  forward,  ancl  put  in  place 
at  the  other  end  of  its  set  of  forms.  Twelve  men  were  re- 
quired to  take  down  and  transport  one  of  the  front  form  sec- 
tions. 

In  setting  up  a  front  form,  its  inner  toe  was  firmly  sup- 
ported by  a  stake  driven  into  the  ground  and  by  the  hori- 
zontal board,  nailed  transversely  under  the  bottom  4  x  4-in. 
horizontal  stringers,  which  rested  on  the  ground.  The  upper 
part  of  the  form  was  then  securely  fastened  to  the  2  x  6-in. 
posts  of  the  back  forms  by  temporary  wooden  connecting 
strips,  which  were  removed  as  the  concrete  filling  was  carried 
up.  The  sections  of  the  front  forms  were  also  securely  tied 
to  each  other. 


RESERVOIRS    AND    TANKS.  607 

A  facing  of  gravel  concrete,  rich  in  cement  and  with  no 
pebbles  larger  than  y2-in.  was  placed  on  the  front  face  of  the 
wall,  extending  from  the  back  edges  of  the  vertical  reinforcing 
bars  to  the  surface.  A  sheet-iron  plate,  about  8  ins.  wide  by 
5  ft.  long,  was  placed  vertically  just  back  of  those  bars.  The 
concrete  was  shoveled  in  loose  to  the  top  of  these  iron  plates, 
and  then  the  mortar  was  poured  in  between  the  latter  and  the 
front  face  forms  from  buckets.  The  iron  plates  were  next 
drawn  by  handles  attached  to  them,  and  the  mortar  and  con- 
crete tamped  together  before  either  had  set.  In  making  joints, 
the  old  concrete  surfaces  were  always  brushed  and  wet  down, 
and,  if  necessary  slushed  with  a  grout  of  neat  cement  before 
new  concrete  was  laid  on  them. 

Construction  of  Floor. — The  excavation  over  the  site  of  the 
reservoir  floor  was  brought  accurately  to  grade  6  ins.  below 
the  surface  of  the  finished  concrete  by  hand  after  the  scoop- 
bucket  excavator  had  passed  over.  In  making  the  excava- 
tion the  levels  were  given  on  radial  lines  drawn  from  the 
ends  of  the  lo-ft.  sections  of  the  wall  to  the  center.  A  rod, 
on  which  the  elevations  of  the  subgrade  at  every  10  ft.  from 
the  wall  to  the  center  of  the  reservoir  were  clearly  marked, 
was  used  in  connection  with  a  transit  on  the  center  post  in 
locating  the  elevations  of  different  points  in  the  reservoir 
floor.  By  using  this  method  the  elevations  required  were 
easily  found  by  the  foreman  in  charge  without  the  assistance 
of  an  engineer.  When  the  work  approached  the  center,  the 
post  was  removed  and  the  transit  was  placed  on  a  portable 
pedestal  which  was  set  on  points  of  known  elevation  on  the 
finished  concrete. 

The  slanting  surface  left  on  the  top  of  the  footing  inside  the 
wall  formed,  together  with  the  projecting  reinforcement  rods, 
an  excellent  bond  between  the  concrete  of  the  wall  and  that 
of  the  floor,  when  the  latter  was  laid.  A  circular  strip  of  the 
floor,  16  ft.  wide,  was  put  down  next  to  the  wall  first,  and 
the  remainder  of  the  floor  was  laid  according  to  the  progress 
of  the  excavation.  The  lower  3^  ins.  of  the  concrete  was 
usually  first  spread  out  over  an  area  12  or  16  ft.  square,  then 
the  reinforcement  was  placed,  and  after  that  the  top  2  ins.  of 
concrete  and  a  l/2-m.  sidewalk  finish  surface  were  laid. 


6o8 


CONCRETE    CONSTRUCTION. 


The  l/4~m.  rods  in  the  bottom  are  6  Ins.  on  centers  in  both 
directions.     They  were   in    12   and    i6-ft.   lengths   and   were 


Fig.    279.— Standpipe    at    Haverhill,    Mass. 

partly  woven  together  in  mats  before  being  placed.    The  rods 
in  one  direction  were  all  laid  out  and  woven  with  four  or 


RESERVOIRS    AND    TANKS.       *  609 

five  of  those  in  the  other  direction,  the  joints  being  tied  with 
small  wire.  The  remaining  cross  rods  were  laid  after  the  mat 
had  been  placed.  The  mats  were  overlapped  I  ft.  This 
method  of  placing  proved  economical  and  efficient,  giving  at 
the  same  time  something  permanent  on  which  to  lay  the  re- 
maining concrete. 

STANDPIPE     AT     ATTLEBOROUGH,     MASS.— The 

stand  pipe  was  50  ft.  in  diameter  and  106  ft.  high  inside,  with 
walls  18  ins.  thick  at  the  bottom  and  8  ins.  thick  at  the  top. 
Figure  279  shows  the  general  arrangement  of  the  reinforce- 
ment. Round  bars  of  0.4  carbon  steel  were  used ;  the  bars 
came  in  56^ -ft.  lengths,  so  that  three  lengths  with  laps  of 
30  ins.,  made  a  complete  ring  around  the  tank.  The  concrete 
was  a  1-2-4  mixture  of  %  to  i/^-in.  broken  stone  with  screen- 
ings used  as  portion  of  sand. 

The  floor  was  built  first,  and  on  it  was  erected  a  tower  to  a 
height  of  60  ft.  and  a  derrick  with  a  4O-ft.  boom  was  set  on 
its  top.  The  derrick  was  operated  by  an  engine  on  the  ground 
which  also  had  a  revolving  gear  attached.  When  the  work 
had  reached  the  top  of  this  tower,  the  tower  was  raised  to 
no  ft.  in  height  and  the  derrick  shifted  to  the  new  elevation. 
The  forms  were  convex  and  concave  sections  7^2  ft.  high  and 
about  II  ft.  long.  The  concave  or  outside  forms  were  made 
in  16  panels,  with  horizontal  ribs  and  vertical  lagging;  two 
complete  rings  of  panels  were  used.  The  panels  were  joined 
into  a  ring  by  clamps  across  the  joints,  this  clamping  action 
and  the  friction  of  the  concrete  holding  them  in  place.  The 
inside  forms  consisted  of  vertical  ribs  carrying  horizontal 
lagging  put  in  place  a  piece  at  a  time  as  the  filling  proceeded. 
They  were  supported  by  staging  from  the  derrick  tower.  The 
remaining  plant  comprised  a  Sturtevant  roll  jaw  crusher  feed- 
ing to  screens  which  discharged  fines  below  %-in.  into  one 
bin,  medium  stone  into  another  bin  and  coarse  stone  into  a 
third  bin.  These  bins  fed  to  the  measuring  hopper  of  a 
Smith  mixer,  which  discharged  into  the  derrick  bucket. 

The  mode  of  procedure  was  as  follows:  The  reinforcing 
rings  were  erected  to  a  height  of  7^  ft.  The  bars  were  bent 
by  being  pulled  through  a  tire  binder  and  around  a  curved 
templet  by  a  steam  engine.  The  bending  gave  some  trouble, 


6io  CONCRETE    CONSTRUCTION. 

due,  it  was  th'ought,  to  the  stiffness  of  the  high  carbon  steel. 
Vertical  channels  4  ins.  deep  were  set  with  webs  in  radial 
planes  or  across  wall  at  four  points  in  the  circumference.  The 
flanges  of  these  channels  were  punched  exactly  to  the  vertical 
spacing  of  the  reinforcing  rings.  Through  the  punched  holes 
were  passed  short  bars  on  the  opposite  ends  of  which  the  rein- 
forcing rings  were  supported  and  wired.  The  three  sections 
of  rod  of  which  each  ring  was  composed,  were  lapped  30  ins. 
and  connected  by  Crosby  clips.  Considerable  difficulty  was 
had  in  holding  the  reinforcing  rings  in  line  by  the  method 
employed ;  it  is  stated  by  the  engineer  that  a  greater  number 
than  four  channels  would  have  been  much  better. 

The  reinforcement  being  in  place,  an  inside  and  an  out- 
side ring  of  forms  was  erected.  Concreting  was  then  carried 
on  simultaneously  from  four  points  on  the  circumference  and 
a  ring  7^2  ft.  high  was  concreted  in  one  operation.  Several 
facts  were  brought  out  in  the  concreting;  careful  and  con- 
scientious spading  was  necessary  to  get  a  smooth  dense  sur- 
face; a  too  wet  mixture  allowed  the  stone  to  settle  and  seg- 
gregate;  care  was  necessary  in  this  thin  wall  containing  two 
rings  of  bars  to  keep  the  stone  from  wedging  among  and 
around  the  bars  and  thus  causing  voids.  The  engineer  states 
that  for  this  reason  the  substitution  of  mortar  for  concrete 
in  tank  walls  is  worth  considering.  He  estimates  that  in  this 
work,  costing  $35,000,  that  the  use  of  a  1-2  mortar  in  place 
of  the  1-2-4  concrete  would  have  increased  the  cost  by  $2,300, 
a  I-2J/2  mortar  by  $1,500,  and  a  1-3  mortar  by  $750.  It  was 
also  found  that  there  was  danger  from  a  movement  of  the  re- 
inforcement in  the  concrete  and  of  the  forms  in  placing  the 
concrete. 

When  a  ring  of  wall  7^  ft.  high  had  been  concreted,  the 
reinforcement  was  placed  as  before  described  for  another  ring. 
The  two  rings  of  forms  below  those  just  filled  were  removed 
from  the  wall,  hoisted  up  and  set  in  place  on  top.  These  two 
operations  of  placing  reinforcement  and  setting  forms  for 
another  ring  of  wall  took  three  days,  so  that  the  top  surface 
of  the  wall  to  which  new  concrete  was  to  be  added,  had  be- 
come hard.  This  hard  surface  was  very  thoroughly  washed 
and  then  coated  with  neat  cement  immediately  before  de- 
positing the  fresh  concrete.  Water  was  admitted  to  the  tank 


RESERVOIRS    AND    TANKS.  6ll 

as  the  work  progressed,  being  kept  about  20  ft.  below  the 
work  in  progress.  Numerous  small  leaks  developed,  but  only 
two  were  large  enough  for  the  water  to  squirt  beyond  the 
face  of  the  wall.  These  leaks  appeared  to  grow  smaller  as 
time  went  on.  To  do  away  with  them  entirely,  the  inside 
wall  was  plastered.  The  first  coat  of  plaster  was  not  suc- 
cessful in  stopping  the  leaks,  so  the  standpipe  was  emptied 
and  replastered,  five  coats  being  used  in  the  lower  20  ft.  This 
did  not  serve  so  resort  was  had  to  a  Sylvester  wash.  A  boiling 
hot  solution  of  12  ozs.  to  the  gallon  of  water  of  pure  olive  oil 
castile  soap  was  applied  to  the  dry  wall.  In  24  hours  this 
was  followed  with  a  2  ozs.  to  the  gallon  solution  of  alum  ap- 
plied at  normal  temperature.  Four  coats  of  each  solution  were 
applied,  which  reduced  the  leakage  to  a  small  amount.  To  do 
away  with  all  leakage  another  four-coat  application  of  Syl- 
vester wash  was  used. 

Details  of  the  cost  of  the  work  are  not  available.  There  were 
770  cu.  yds.  of  concrete  in  the  walls  and  185  tons  of  steel 
bars.  Altogether  3,000  Crosby  clips,  costing  $1,100  were  used. 
The  cost  of  the  concrete  in  place  was  about  as  follows : 

Cement,  per  cu.  yd.  of  concrete    $  4.80 

Sand  and  stone,  per  cu.  yd.  of  concrete 3.90 

Mixing,  per  cu.  yd.  of  concrete - 0.40 

Placing,  per  cu.  yd.  of  concrete 2.20 

Forms,  per  cu.  yd.  of  concrete 2.65 

Total  per  cu.  yd.  of  concrete $13-95 

GAS  HOLDER  TANK,  DES  MOINES,  IOWA.— The 
tank  was  84  ft.  in  diameter  and  21  ft.  5  ins.  deep.  It  had  a 
horizontal  floor  16  ins.  thick  5  ft.  below  ground  level  and  a 
wall  21  ft.  high,  18  ins.  thick  at  base  and  12  ins.  thick  at  top 
under  coping  and  with  alternate  pilasters  and  piers  around 
the  outside.  The  concrete  for  the  floor  was  a  1-2^-5  2-in. 
stone  mixture  and  the  concrete  for  the  walls  was  a  1-2-4  i-in. 
stone  mixture.  The  floor  was  contructed  first,  with  a  circu- 
"  lar  channel  for  the  wall  footing,  and  then  the  wall  was 
structed. 


612 


CONCRETE    CONSTRUCTION. 


Piles  were  driven  in  the  bottom  and  their  heads  cut  to  level 
and  filled  around  with  tamped  cinders.  Two  circumferential 
rows  of  posts  were  driven  around  the  edge  so  that  a  pair  of 
posts,  one  inner  and  one  outer,  came  on  each  radius  through  a 
wall  pilaster  or  pier.  These  posts  served  primarily  to  carry 
the  frames  for  the  wall  forms  and  secondarily  for  holding  the 
forms  for  the  circular  wall  footing  channel  as  shown  by  the 
sketch  Fig.  280.  The  floor  concrete  was  put  in  in  diamond- 
shaped  panels  between  forms,  whose  top  edges  were  set  to 
floor  level.  Each  form  was  designed  to  make  a  groove  in  the 
edge  of  the  slab  so  that  adjacent  slabs  would  bond  with  it. 


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'  X-  °i'  j  .  . 

0.    -  Q  '     Q 

Fig.  280.— Forms  for  Constructing  Channel  for  Wall  in  Reservoir   Floor. 

The  concrete  was  wheeled  to  place  in  barrows,  thoroughly 
tamped,  roughly  floated  to  surface  and  finally  given  a  trowel 
finish. 

To  construct  the  walls,  the  posts  before  mentioned,  were 
cut  off  to  exact  level  6  ins.  above  the  finished  floor.  A  bent 
for  the  wall  forms  was  then  erected  on  each  radial  pair  as 
shown  by  Fig.  281.  The  bents  were  erected  by  hand  and 
carefully  plumbed  and  lined  up,  both  radially  and  circum- 
ferentially.  The  pier  and  pilaster  forms  were  then  erected 
across  wall  opposite  each  bent  as  shown  by  Fig.  281.  The 
forms  for  the  wall  between  pilasters  and  piers  consisted  of 


RESERVOIRS    AND    TANKS. 


613 


panels  4  ft.  high.  A  panel  for  the  inner  face  of  the  wall  is 
shown  by  Fig-.  282,  the  panel  for  the  outer  face  was  similar 
in  construction  but  was,  of  course,  concave  instead  of  convex. 
Enough  panels  of  each  kind  were  made  to  reach  entirely 


Fig.    281.—  Frame    for    Forms    for    Circular    Reservoir    Wall. 

around  the  tank.  The  inside  panels  were  bolted  at  the  ends 
to  the  uprights  of  the  bents  ;  the  outside  panels  were  similarly 
lag  screwed  to  the  uprights  of  the  pier  and  pilaster  forms; 
Fig.  281  shows  the  holes  for  bolts  and  lag  screws.  The 


31 'Eye  End 
Fig.    282. — Form   Panels  for  Circular   Reservoir  Wall. 

spaces  between  ends  of  inside  panels  in  front  of  the  bents  was 
closed  by  a  l/2  x  6-in.  steel  plate  the  full  height  of  the  wall ; 
this  plate  was  bolted  to  the  bents  and  had  anchor  bolts  every 
3  ft.,  reaching  into  the  wall.  This  anchoring  of  the  plate  to 
the  wall  permitted  the  diagonal  bracing  of  the  bents  to  be 


614 


CONCRETE    CONSTRUCTION. 


removed  to  allow  runways  to  be  laid  on  the  cross-pieces,  since 
the  plate  held  firmly  the  bent  post  to  which  it  was  bolted  as 
indicated  by  Fig.  283.  A  complete  circle  of  inside  and  outside 
forms  was  erected  and  filled,  then  the  forms  were  raised  3  ft. 
by  block  and  tackle  from  cross  timbers  across  wall  between 
bent  and  pilaster  form,  and  this  depth  concreted  and  the 
forms  raised  again.  The  forms  were  oiled  on  the  faces  com- 
ing against  the  concrete.  It  took  about  half  a  day  to  raise 
and  set  a  complete  circle  of  forms.  The  concrete  was  mixed 
outside  the  tank  and  was  wheeled  up  inclines  and  dumped 
onto  runways  lai'd  on  the  cross  pieces  of  the  bents  and  then 
loaded  and  wheeled  to  place.  The  runway  was  raised  to  suc- 
cessive horizontals  as  the  work  progressed. 

Only  a  few  general  cost  figures  are  available.    The  labor  for 
mixing  and  placing  concrete  was  as  follows : 


2//x4,,T^r 

Fig.    283.— Sketch    Showing    Filler    for    Joint    Between    Form    Panels. 

For  floor,  per  cu.  yd 3.4  hrs. 

For  walls,  per  cu.  yd 5.2  hrs. 

For  cornice,  per  cu.  yd 5.4  hrs. 

The  cost  of  unloading  the  reinforcing  steel  from  cars  and 
placing  it  in  the  structure  was  $7  per  ton,  or  0.35  ct.  per  Ib. 
The  cost  of  form  lumber,  framing,  erecting  and  taking  down 
forms  was  9  cts.  per  square  foot  of  wall  covered. 

GAS  HOLDER  TANK,  NEW  YORK  CITY.— The  tank 
for  the  Central  Union  Gas  Co.'s  gas  holder  at  i36th  St.  and 
Locust  Ave.  has  an  interior  diameter  of  189  ft.  and  a  depth 
of  41  ft.  6  ins.  The  exterior  wall  is  42  ft.  6  ins.  deep,  5  ft.  6 
ins.  thick  at  the  base  and  4  ft.  6  ins.  thick  at  the  top;  con- 
centric with  it  and  n  ft.  6  in.  away  is  the  interior  wall  166  ft. 
in  external  diameter  and  16  ft.  6  ins.  high  with  a  uniform 


RESERVOIRS    AND    TANKS. 


615 


thickness  of  2  ft.  6  ins.  The  bottom  of  the  tank  enclosed  by 
the  interior  wall  is  a  truncated  cone  whose  base  is  at  the  level 
of  the  wall  top.  Fig.  284  shows  the  arrangement. 

It  was  specified  that  the  diameter  of  this  tank  should  not 
vary  more  than  2  ins.  and  that  the  exterior  wall  should  not 
vary  more  than  I  in.  from  the  vertical.  The  main  form  was  a 
circular  drum  whose  exterior  face  formed  the  inner  face  of 
the  main  wall.  Its  framework  consisted  of  40  vertical  trusses 
or  radial  frames  6  ft.  deep  and  42  ft.  high  set  equidistant 
around  the  tank,  these  trusses  being  braced  together  on  both 
edges  by  circumferential  timbers.  Radial  horizontal  pieces 
nailed  across  the  radial  frames  and  projecting  beyond  their 
faces  carried  vertical  iron  guide  strips  against  which  the 


Fig.   2S4.— Section  of  Gas  Holder  Tank,  New  York  City. 

movable  panels  of  lagging  were  seated.  These  panels  were 
cylindrical  segments  5  ft.  high  and  long  enough  to  span  be- 
tween two  radial  frames  or  14  ft.  n^$  ins.  The  panels  were 
adjusted  radially  by  wedges  to  give  l/%  in.  clearance  in  respect 
to  inner  face  of  wall ;  enough  of  them  were  made  to  form  a 
complete  circle  and  they  were  set  with  i-in.  clearance  be- 
tween vertical  edges  of  adjacent  panels  to  allow  for  swelling 
when  wetted. 

The  concrete  bottom  of  the  annular  space  between  walls 
was  first  constructed.  On  this  floor  were  set  6  x  6-in.  x  8-ft. 
sills  for  the  radial  frames;  these  were  located  accurately  by 
transit.  The  radial  frames  were  then  set  on  the  sills  by  a 
derrick,  adjusted  to  exact  radial  position  by  a  measuring  wire 


616  CONCRETE    CONSTRUCTION. 

iswiveled  to  the  center  point  of  the  tank  and  plumbed  by 
transit.  A  complete  circle  of  lagging  panels  was  then  ad- 
justed to  the  frames  at  the  bottom  of  the  trench.  For  con- 
creting, the  wall  was  divided  circumferentially  into  three  sec- 
tions. These  sections  were  separately  concreted  to  the  top  of 
the  lagging  panels,  that  is  to  a  height  of  5  ft.  After  the  con- 
crete had  set  48  hours  the  panels  were  hoisted  4  ft.,  so  that 
their  lower  edges  still  overlapped  the  concrete  12  ins.,  and 
another  ring  of  wall  was  concreted.  This  procedure  was  re- 
peated until  the  wall  was  completed.  The  back  of  the  wall 
was  formed  against  the  side  of  the  trench  where  possible  and 
in  other  places  against  rough  board  lagging  held  in  position 
in  any  convenient  way. 

For  handling  the  concrete,  four  equidistant  panels  of  the 
form  framework  were  converted  into  double  compartment 
elevator  shafts  providing  for  two  balanced  cars  controlled  by 
a  sheave  provided  with  a  friction  brake.  Three  mixers  sup- 
plied concrete  to  these  elevators.  Considering  a  single  ele- 
vator, two  barrows  of  concrete  were  wheeled  from  the  mixer 
onto  the  car  at  the  top  of  the  elevator  frame,  the  friction 
brake  was  released  and  the  loaded  car  descended  to  the  work 
hoisting  at  the  same  time  its  twin  car  loaded  with  two  empty 
barrows.  The  elevators  distributed  to  wheeling  platforms 
cantilevered  out  from  the  outer  face  of  the  framework  and 
located  successively  5  ft.,  15  ft.,  20  ft.,  etc.,  above  the  bottom 
of  the  trench.  On  these  platforms  the  concrete  was  dis- 
tributed as  required,  the  maximum  wheeling  distance  being 
never  over  one-eighth  the  circumference  of  the  tank.  The 
concrete  was  mixed  very  wet  and  deposited  in  6-in.  layers. 

The  inner  and  outer  surfaces  of  the  wall  were  both  painted 
with  two  coats  of  stiff  cement  grout  neat,  and  in  addition  the 
inner  surface  was  rubbed  smooth  by  carborundum  brick.  Re- 
garding this  finishing  work  Mr.  Howard  Bruce,  Engineer  of 
Construction,  writes: 

"The  scouring  was  done  on  each  section  of  the  wall  imme- 
diately after  the  forms  supporting  these  sections  had  been 
removed.  The  object  was  to  rub  this  interior  surface  with 
carborundum  before  the  surface  of  the  concrete  had  taken  its 
final  set.  By  rubbing  the  concrete  at  this  stage  and  at  the 
same  time  applying  witu  a  brush  a  coating  of  neat  cement 


RESERVOIRS    AND    TANKS.  617 

grout,  we  believe  the  face  of  the  concrete  was  made  more  or 
less  impermeable,  as  examination  shows  the  pores  of  the 
concrete  are  very  largely  filled  up.  We  have  no  accurate 
figures  as  to  the  cost  per  square  yard  of  this  treatment,  but 
one  can  readily  see  that  this  cost  would  be  insignificant  as 
compared  with  the  possible  improvement  of  the  work.  The 
carborundum  brick  was  selected  on  account  of  its  hardness. 
I  believe  practically  any  stone  would  answer  the  same  pur- 
pose. In  addition  to  filling  the  pores  of  the  concrete,  this 
treatment  gives  the  surface  a  good  smooth  finish." 

LINING  A  RESERVOIR,  QUINCY,  MASS.— The  follow- 
ing methods  and  costs  are  given  by  Mr.  C.  M.  Saville,  M.  Am. 
Soc.  C.  E.,  for  lining  the  Forbes  Hill  Reservoir  at  Quincy, 


Fig.    285.— Section    of   Reservoir   Lining,    Quincy,    Mass. 

Mass.     This  reservoir  is  100  x  280  ft.  on  the  floor,  with  side 
slopes  of  i  on  1.75,  and  was  built  by  contract  in  1900-1901. 

Figure  285  is  a  section  of  the  concrete  lining;  the  bottom 
layer  for  the  floor  was  a  1-2-5  natural  cement  concrete,  and  for 
the  sides  a  i-2l/2-6l/2  Portland  cement  concrete ;  the  top 
layer  on  both  floor  and  sides  was  a  1-2^-4  Portland  cement 
concrete;  2l/2-m.  stone  was  the  maximum  size  allowed  in  any 
concrete  and  il/2-m.  the  maximum  allowed  in  the  top  layer. 
Smaller  stone  was  used  for  special  surface  work,  as  noted 
further  on.  The  stone  was  cobbles  turned  up  in  the  exca- 
vation work  and  had  to  be  gathered  from  scattered  piles  and 
washed  before  crushing.  A  9x15  Farrel  crusher,  operated 
by  a  12  HP.  engine  did  the  crushing;  it  was  rated  at  125  tons 


618  CONCRETE    CONSTRUCTION. 

a  day,  but  averaged  only  about  40  tons.  The  fine  dust  was 
screened  out  and  the  remainder  discharged  into  a  3O-cu.  yd., 
three-compartment  bin,  one  compartment  for  stone  less  than 
1 5/2  ins.,,  another  for  il/2  to  2l/2-m.  stone  and  a  third  for 
returns.  <  The  stone  had  46  per  cent,  voids  and  weighed  95  Ibs. 
per  cu.  ft.  The  sand  was  of  excellent  quality.  Atlas  and 
Beach's  Portland  and  Hoffman  natural  cement  were  used. 

All  concrete  was  mixed  and  placed  by  hand,  the  concrete 
gang  consisting  generally  of  i  sub-foreman,  2  men  measuring 
materials,  2  men  mixing  mortar,  3  men  turning  concrete  three 
times,  3  men  wheeling  concrete,  I  man  placing  concrete  and 
2  men  ramming  concrete.  Two  gangs  were  ordinarily  em- 
ployed, each  mixing  and  placing  about  20  cu.  yds.  per  day,  or 
1.43  cu.  yds.  per  man  per  day.  The  materials  (sand  and  stone) 
were  measured  in  bottomless  boxes,  the  following  sizes  being 
used: 

— Sand  Box —  — Stone  Box — 

Prop,  of  Mix.  Size.         Vol.  cu.  ft.         Size.     Vol.  cu.  ft. 

1-2^-4*   2'9"x2'xi'8"          9.25         5'x4'5^"         14.8 

1-3-6*     2'9"X2'X2'  n.i  5'x6'8"  22.2 

1-2-5    2'9"x2'xi'4"          7.4          5'x6'6^"         18.5 

1-2^-6^    2'9"x2'xi'8"          9.25        5'x7'2>4"        24.05 

"These  mixtures  were  used  for  gate  house  and  standpipe  foundation  work. 

The  bottom  layer  was  placed  in  a  continuous  sheet ;  the  top 
layer  was  laid  in  ro-ft.  squares  on  the  floor  and  in  8  x  lo-ft. 
squares  on  the  sides;  these  squares  alternated  in  both  direc- 
tions, one-half  being  first  laid  and  allowed  to  set.  In  laying 
the  sides  the  surface  was  left  I  in.  low  and  then  before  the 
concrete  had  set  was  brought  to  plane  by  a  i-in.  layer  of 
1-2^2-4  mixture  using  stone  and  stone  dust  less  than  ^  in. 
The  concrete  for  the  floor  was  mixed  rather  wet  and  rammed 
until  it  quaked ;  on  the  sides  a  drier  mixture  was  necessary  to 
prevent  flow.  The  cost  of  the  lining  concrete  was  as 
follows : 


RESERVOIRS    AND    TANKS.  619 

Bottom  Layer  on  Floor:     1-2-5  Mixture: 

1.25  bbls.  natural  cement  at  $1.08 $1.350 

0.34  cu.  yd.  sand   at   $i  .02 0.347 

0.86  cu.  yd.  stone  at  $1.57 I-35O 

4l/2  ft.  B.  M.  lumber  at  $20  per  M 0.090 

Labor,    on    forms    t  o.ioo 

Labor  mixing   and   placing    1.170 

Labor  general   expenses 0.080 

Total $4.487 

Bottom  Layer  on  Sides:     i-2y2-6l/2  Mixture: 

1.08  bbl.  Portland  cement  at  $1.53 $1.652 

0.37  cu.  yd.  sand   at   $1.02 0.377 

0.96  cu.  yd.  sone    at   $1.57 1.507 

Lumber  for  forms  (about  i  ft.  B.  M.)  at  $20 0.016 

Labor,  on   forms 0.121 

Labor,  mixing  and  placing  1.213 

Labor,  general  expenses 0.177 

Total $5.063 

Top  Layer  on  Floor  and  Sides:     1-2^-4  Mixture: 

1.37  bbls.   Portland  -cement  at  $1.53 $2.09 

0.47  cu.  yd.  sand   at   $1.02 0.48 

0.75  cu.  yd.  stone  at  $1.57 ' 1.17 

i2l/2  ft.  B.  M.  form  lumber  at  $20  per  M 0.25 

Labor,  on  forms 0.26 

Labor,  mixing  and   placing    !-53O 

Labor,  general  expenses   0.150 

Total    $5.93 

The  side  finish  with  1-2^-4  concrete  of  }i-in.  stone  cost 
$0.154  per  sq.  yd.  i  in.  thick.  This  work  was  done  by  a  gang 
of  3  plasterers  and  3  helpers. 

The  layer  of  plaster  between  the  concrete  layers  was  put 
down  on  4-ft.  strips  and  finished  similarly  to  the  surface  of  a 
granolithic  walk.  This  layer  consisted  of  1-2  mortar  fin- 
ished with  a  4-1  mortar.  To  keep  the  plaster  from  cracking  it 
was  covered  with  strips  of  coarse  burlap  soaked  in  water; 
this  precaution  was  not  entirely  successful,  some  cracks  ap- 


620  CONCRETE    CONSTRUCTION. 

peared  and  had  to  be  grouted.  Three  gangs,  each  consisting 
of  i  plasterer  and  I  helper,  did  the  plastering,  each  gang  lay- 
ing about  700  sq.  yds.  per  day.  The  cost  of  the  plaster  layer 
was  as  follows : 

Item.  Per  100  sq.  ft.     Per  sq.  yd.     Per  cu.  yd. 

Cement  at  $1.53 $1.15  $0.103  $742 

Sand  at  $1.02 0.13  0.012  0.86 

Burlap    0.02  0.002    ,  0.14 

Labor    0.92  0.083  6.00 


Totals   $2.22  $0.200  $14,42 

It  will  be  noted  that  it  took  over  5  bbls.  of  cement  per  cubic 
yard,  and  that  the  labor  cost  was  $6  per  cubic  yard. 

RELINING  A  RESERVOIR,  CHELSEA,  MASS.— The 
following  account  of  relining  the  Powder  Horn  Hill  Reser- 
voir at  Chelsea,  Mass.,  is  taken  from  a  paper  by  Mr.  C.  M. 
Saville.  This  reservoir  which  holds  about  1,000,000  gallons  is 
oval  in  shape,  98  x  175  ft.  at  the  top,  68  x  148  ft.  at  the  bottom 
and  15  ft.  deep,  with  side  slopes  about  I  on  i.  The  work  was 
done  by  day  labor.  For  sake  of  completeness  the  costs  of 
excavation  and  back-filling  are  given  here  as  well  as  the  con- 
crete costs. 

The  top  of  the  bank  was  too  narrow  to  allow  the  use  of 
carts  and  an  i8-in.  gage  railroad  was  decided  upon  as  most 
convenient  for  handling  materials.  A  65-ft.  boom  derrick  with 
a  7o-ft.  mast  was  used  for  removing  the  excavated  material 
and  for  depositing  concrete.  The  derrick  was  operated  by  a 
15-h.p.  double  drum  hoisting  engine,  was  held  in  place  by  six 
wire  guy  ropes,  and  had  a  reach  such  that  only  one  moving 
was  necessary  after  it  was  placed.  The  engine  and  derrick 
were  set  up  on  the  floor  of  the  reservoir,  and  the  work  of 
excavation  was  begun  at  about  the  middle  of  the  south  side. 
In  order  to  facilitate  the  work,  a  platform  supported  on  A 
frames  was  set  up.  These  frames  were  spaced  about  15  ft. 
apart  and  rested  on  the  bottom  and  slope  of  the  reservoir, 
being  held  in  place  by  bolts  driven  into  the  floor. 

The  paving  blocks  on  the  top  of  the  slope  were  removed  and 
piled  up  to  be  taken  away.  The  old  lining  and  the  material 
excavated  from  the  bank  were  shoveled  into  the  scale  pan  of 


RESERVOIRS    AND    TANKS.  621 

the  derrick,  hoisted  to  the  cars  on  the  top  of  the  bank,  and 
then  run  by  gravity  to  a  dump  a  short  distance  down  the  hill- 
side. Here  the  cars  were  run  out  on  a  rough  trestle,  the  load 
dumped,  and  the  empties  hauled  back  to  the  work  by  a  rope 
carried  through  pulleys  to  the  winch  head  on  the  hoisting 
drum  of  the  engine. 

For  the  storage  of  some  of  the  materials,  two  small  portable 
storehouses  were  set  up — one  8  x  10x7  ft.,  the  other  n  x  i6x 
7  ft.  The  bulky  portions,  such  as  cement,  sand,  and  stone, 
were  delivered  as  necessary,  a  few  days'  supply  only  being 
kept  on  hand.  A  branch  from  the  railroad  was  so  arranged 
that  it  passed' the  storehouses  and  stone  piles,  while  the  sand 
was  piled  close  to  the  concrete  mixing  board.  The  intention 
on  the  work  was  to  do  nothing  by  hand  that  could  possibly  be 
done  by  steam,  except  that  all  of  the  concrete  was  mixed  by 
hand.  As  great  a  proportion  of  water  was  used  as  could  be 
done  without  causing  the  material  to  slide  when  rammed  in 
place. 

The  lower  layer  of  concrete  was  of  the  'proportion  by  vol- 
ume of  I  cement,  2^  sand,  and  6l/2  crushed  stone  (sizes  from 
Y^  to  il/2  ins.).  This  was  rather  a  lean  mixture,  and  as  it 
could  not  be  rammed  enough  to  flush  all  over,  the  surface  was 
finished  where  necessary  by  a  thick  mortar  made  in  the  pro- 
portion of  I  cement  to  6  sand,  and  applied  with  heavy  brushes. 
Before  placing  any  of  the  concrete,  the  bank  back  of  the  old 
concrete  left  in  place  was  thoroughly  rammed  with  iron 
railroad  tampers,  and  the  edge  of  the  old  concrete  was 
scrubbed  with  water  and  a  stiff  brush  and  then  coated  with 
1  to  4  grout,  which  was  allowed  to  fill  in  the  angle  between 
the  concrete  and  the  slope.  Just  before  placing  the  concrete 
the  earth  bank  was  well  wet  in  order  that  moisture  might  not 
be  drawn  from  the  concrete  while  it  was  soft. 

In  order  to  make  the  new  lining  as  waterproof  as  possible, 
a  layer  of  asphalt  was  placed  on  top  of  the  lower  layer  of  con- 
crete and  brought  up  on  the  exposed  edge  of  the  old  layer 
at  the  bottom  of  the  new  work.  This,  it  was  expected  would 
make  an  elastic  and  watertight  joint  between  the  new  and  the 
old  work. 


622  CONCRETE    CONSTRUCTION. 

Venezuela  asphalt,  "Crystal  Brand,"  was  used,  being  poured 
upon  the  top  of  the  concrete  layer  a*nd  allowed  to  run  down 
the  slope,  care  being  taken  that  the  concrete  was  entirely  and 
perfectly  covered.  After  the  first  layer  of  asphalt  was  cool, 
a  second  layer  was  similarly  applied,  and  the  resulting  sheet 
was  about  }4  in-  thick.  Any  inclination  to  crawl  down  the 
slope  when  exposed  to  the  sun  was  readily  stopped  by  throw- 
ing on  a  pailful  of  cold  water.  A  most  particular  part  of  this 
work  was  to  get  the  asphalt  as  hot  and  liquid  as  possible  and 
yet  not  burn  it.  All  of  the  concrete  was  protected  from  the 
sun  and  kept  damp  by  being  covered  with  strips  of  burlap, 
which  were  moistened  by  sprinkling. 

The  upper  layer  of  concrete  was  composed  of  a  much  richer 
mixture  of  concrete  than  that  used  in  the  bottom  layer,  the 
proportions  by  volume  being  I  cement,  ij4  sand,  ij4  stone 
dust,  and  4  broken  stone  of  the  sizes  mentioned  above.  On 
account  of  the  steep  slope  it  was  possible  to  do  only  a  little 
ramming,  and  the  material  was  laid  as  wet  as  possible.  To 
make  this  layer  more  impervious  and  also  to  obtain  a  smooth 
surface,  the  concrete  was  left  about  an  inch  below  and  a 
finish  coat  applied  by  expert  granolithic  finishers.  This  coat- 
ing was  applied  as  soon  as  it  was  possible  to  do  so  after  the 
main  layer  was  in  place,  but  on  account  of  the  steepness  and 
the  liability  of  the  wet  concrete  to  flow,  care  had  to  be  taken 
not  to  begin  work  too  soon. 

The  top  finishing  coat  was  made  in  the  proportion  of  I  part 
cement,  \2/$  part  sand,  and  3^3  parts  stone  dust.  In  order 
to  help  in  bonding,  the  last  ramming  on  the  concrete  was  done 
with  rammers  studded  with  pieces  of  iron  about  I  in.  long 
and  J"£  in.  deep. 

The  finishing  was  done  in  three  operations:  The  material 
was  spread  on  the  concrete  and  thoroughly  worked  into  it  by 
the  finishers,  using  rough  wooden  floats ;  after  this  it  was 
gone  over  and  partially  smoothed  down  with  a  thin  steel  float ; 
and  finally  it  was  worked  to  give  the  finished  appearance  and 
an  impervious  surface. 

The  under  layer  of  concrete  was  placed  in  a  continuous 
sheet.  The  upper  layer  was  put  down  in  alternate  strips,  10 
ft.  long  (the  whole  length  of  the  layer)  and  5  ft.  wide.  These 
blocks  were  built  up  in  forms,  which  were  not  removed  until 


RESERVOIRS    AND    TANKS.  623 

the  concrete  had  set.  Filially,  the  back  or  edge  of  the  block 
toward  the  bank  was  well  wet  and  thoroughly  plastered,  to 
prevent,  as  far  as  possible,  the  infiltration  of  any  water. 
The  plaster  was  mixed  in  the  proportion  of  I  part  cement 
to  4  parts  sand.  When  the  forms  were  wholly  removed,  the 
space  between  the  concrete  and  the  bank  was  refilled,  to 
within  about  6  ins.  of  the  top,  with  a  clayey  material  pre- 
viously excavated,  and  the  space  was  filled  and  graded  to  the 
top  of  the  bank  with  loam.  During  the  work  two  holidays 
intervened;  the  men  were  also  transported  to  and  from  the 
work.  Charges  were  made  for  these  items,  amounting  to 
$209.77,  and  this  sum,  together  with  the  cost  of  installing  the 
plant  ($716.03)  are  oroportionally  charged  against  the  work 
as  follows : 

Per  cent.  Total.         Per  cu.  yd. 

Excavation     70.3  $651  $2.17 

Lower  concrete    12  in  1.16 

Upper    concrete    15.4  143  i.n 

Back  fill    2.3  21  .28 

The  detailed  cost  of  repairing  the  reservoir  lining  is  given 
in  the  following  tabulations : 

Excavation. 

Rate.     Per  cu.  yd. 

Foreman    9  5/9  days  $4.00  $0.13 

Engineman 12  3/9  days  3.00  .12 

Carpenter    2         days  2.67  .02 

Laborers    9  6/9  days  2.25  .07 

Laborers    no  2/9  days  2.00  .73 

Laborers   46  5/9  days  1.75  .27 

Derrick    123/9  da7s  3-75  -r5 

Rails  and  cars  112/9  days  °-4°  '°2 

Stove  coal  3.05  tons  6.50  .07 

Egg  coal 95  tons  6.25  .02 

Total,  300  cu.  yds $i-6o 

Estimated  proportionate  charge  for  plant  installation  and 
holidays    . .  < 2>I7 

Grand  total $377 


624  CONCRETE    CONSTRUCTION. 

Lower  Layer  Concrete. 

Rate.     Per  cu.  yd. 

Foreman 3  7/9  days  $4.00  $0.16 

Engineer        2  3/9  days  3.00  0.07 

Carpenters    7         days  2.67  0.20 

Laborers    I  7/9  days  2.25  0.06 

Laborers  89         days  2.00  1.87 

Laborers  .-. 4        days  1.75  0.07 

Derrick  and  engine 2  3/9  days  3.75  0.08 

Rails  and  cars 2  2/9  days  0.40  o.oi 

Cement   106^  bbls.  1.35  1.50 

Sand 37.4  cu.  yds.  i.io  0.43 

Broken  stone   1 17.9  tons  1.35  1.67 

Egg  coal   .41  tons  6.25  0.03 

Lumber    1.3  M.  ft.  21.00  0.28 


Total,  95.5  cu.  yds .$6.43 

Estimated  proportionate  charge  for  plant  installation  and 
holidays    1.16 


Grand  total $7-59 

Upper  Layer  Concrete. 

Rate.     Per  cu.  yd. 

Foreman    6  7/9  days  $4.00  $0.21 

Engineer    I  8/9  days  3.00  0.04 

Carpenter    18  5/9  days  2.67  0.38 

Laborers   i  7/9  days  2.25  0.03 

Laborers   1 19  5/9  days  2.00  1.85 

Derrick  and  engine i  8/9  days  3.75  0.05 

Rails  and  cars 8  3/9  days  0.40  0.03 

Cement 176^2  bbls.  1.35  1.86 

Sand   30.2  cu.  yds.  i.io  0.26 

Stone  dust    41.6  tons  1.50  0.48 

Broken  stone  122.8  tons  1.35  1.28 

Egg  coal   .2  tons  6.25  o.oo 

Lumber   4  M.  ft.  21.00  0.65 

Burlap 300  yds.  0.04^  o.io 

Nails 170  Ibs.  0.05  0.03 

Total,  129.2  cu.  yds $7.25 


RESERVOIRS    AMD    TANKS. 


625 


Estimated  proportionate  charge  for  plant  installation  and 
holidays !€ll 

Grand  total  , , , . , $8.36 

Back  Plaster. 

Rate.  Per  sq.  yd. 

Plasterer    38/9  days  $5.40  $0.08^ 

Plasterer    8/9  days  6.00  0.02 

Plasterer    , 5  5/9  days  4.50  0.09 

Laborers  9  3/9  days  2.25  0.08^ 

Laborers  3/9  days  2.00  o.oo 

Cement   6  bbls.  1.35  0.03 

Sand 3.3  cu.  yds.  i.io  o.oi 

Total,  262  sq.  yds $0.32 

Surfacing. 

Rate.     Per  sq.  yd. 

Plasterer 7  6/9  days  $5.40  $0.09 

Plasterer 2  1/9  days  6.00  0.03 

Plasterer 9  4/9  days  4.50  0.09 

Laborers  12  8/9  days  2.25  0.06 

Laborers  2  4/9  days  2.00  o.oi 

Cement   22  1/4  bbls.  1.35  0.06 

Sand   5.07  cu.  yds.  i.io  0.02 

Stone  dust  14  tons  1.50  0.04 

Total,  460  sq.  yds $0.40 

Asphalt. 

Rate.         Per  sq.  yd. 

Foreman    1/9  day  $4.00  $0.00 

Asphalt  man   n         days  2.00                0.05 

Laborers  6         days  2.00                0.02^ 

Asphalt  kettle n         days  1.50                0.03^ 

Asphalt 3.9     tons  30.00                0.25 

Asphalt  mops  3-°°                ao1 

Total,  464  sq.  yds $0.37 


626  CONCRETE    CONSTRUCTION. 

Back   Filling. 

Rate.     Per  cu.  yd. 

Foreman i  3/9  days  $4.00  $0.07 

Laborers   23  3/9  days  2.00  0.62 

Laborers    9         days  1.75  0.21 

Rails  and  cars 2  2/9  days  0.40  0.02 

Loam    27  5/9  cu.  yds.  1.25  0.46 

Total,  75  cu.  yds .$1.38 

Estimated  proportionate  charge  for  installing  plant  and 
holidays , $0.28 


Grand  total   ...................................  $1.66 

Installing  Plant. 

Total. 

Foreman   ....  ..........   15  4/9  days  $4.00  $  61.78 

Sub-foreman    .  .  ........      I         day  3.00  3.00 

Engineer  ..............     84/9  days  3.00  25.33 

Carpenter   .............     3         days  2.67  8.00 

Watchman   ............  42         days  2.00  84.00 

Laborers   .......  .  ......    17  4/9  days  2.25  38.36 

Laborers    ..............  149  8/9  days  2.00  299.78 

Double  team   ..........    10  1/2  days  5.00  52-5O 

Singe  team  ............     6        days  2.00  12.00 

Single  team   ...........      I         day  3.50  3.50 

Teaming  (total)    .................  ....  53-OO 

Derrick  and  engine  .....    114/9  days  3-75  49-92 

Rails  and  cars  .........     8  2/9  days  0.40  3.29 

Broken  stone   ........           7.05  tons  1.35  9.52 

Egg  coal  ...............  6    ton  6.25  3.75 

Kerosene    ..........  ...            30  gal.  o.i  i  3.30 

Oil    ...................              4  gal.  0.25  i.oo 

Spikes    ................          220  Ibs.  0.05  n.oo 


Total 


The  cost  of  the  concrete  work  in  the  lower  and  upper  layers 
can  be  still  further  detailed  as  shown  below: 


RESERVOIRS    AND    TANKS.  627 

Lower  Layer  Concrete, 
95.5  cu.  yds.,  1-2^-6^  concrete. 
Materials.  Rate.     Per  cu.  yd. 

Atlas  cement    i.n       bbl.             $1.35  $1.50 

Sand    ? 39  cu.  yd.               i.io  0.43 

Broken  stone  (.97  cu.  yd.)      1.23     tons               1.35  1.66 

Miscellaneous,  plant,  coal,  etc 1.28 


Labor : 
fixing  ai 
Carpenter  work  on  forms  at  $24.00  per  M "'TS?! ...     .34 


Mixing  and  placing 4.*.\\  .$2.09 


Total  per  cu.  yd.  in  place $7.36 

Upper  Layer  Concrete. 
129.2  cu.  yds.,  i-i%-i%-4  concrete. 

Materials  :                                                          Rate.  Per  cu.  yd. 

Atlas  cement    1.37       bbl.             $1.35  $1.85 

Sand 24  cu.  yd.               i.io  0.26 

Stone  dust  (.25  cu.  yd.) ...       .32       ton               1.50  0.48 

Broken  stone  (.75  cu.  yd.)       .96       ton               1.35  1.30 

Lumber 031  M.  ft.            21.00  0.65 

Miscellaneous,  plant,  etc 1.32 

Labor : 

Mixing  and  placing   1.85 

Carpenter  work  on  forms  at  $21.00  per  M 0.66 

Total  per  cu.  yd.  in  place   $8.37 

The  following  approximate  labor  costs  are  also  given : 
Transporting,  erecting  and  removing  derrick,  $260.85.  Equiva- 
lent time :  Foreman,  6  days ;  engineer,  4  days ;  laborer,  85 
days. 

Transporting,  laying  and  removing  track,  $125.03.  Equiva- 
lent time :  Foreman,  4  days  ;  laborer,  40  days. 

Caring  for  dump  and  disposing  of  surplus  by  rough  grading, 
$70.28.  Equivalent  time:  Foreman,  i  day;  laborer,  33  days. 

The  total  cost  of  the  work  was  $3,503.66,  divided  up  as 
follows : 


628  CONCRETE    CONSTRUCTION. 

Excavation   $  480.79 

Lower  layer  concrete 614.15 

Upper  layer  concrete 937-94 

Back  plaster 84.73 

Surfacing 186.04 

Asphalting 170.94 

Back  filling 103.27 

Installing  plant 716.03 

Transportation  and  holidays 209.77 


Grand  total .$3,503.66 

LINING  JEROME  PARK  RESERVOIR.— The  bottom  of 
the  reservoir  that  was  lined  covered  250  acres,  and  the  con- 
crete lining  was  6  ins.  thick.  The  lining  was  laid  in  alternate 
strips  16  ft.  wide  between  forms  set  to  grade.  The  concrete 
was  mixed  in  18  Ransome  mixers  provided  with  charging  hop- 
pers and  mounted  on  trucks  without  boilers.  Steam  was  sup- 
plied to  the  mixer  engines  from  the  boilers  of  the  contractor's 
locomotives.  One  locomotive  supplied  steam  for  three  or  four 
mixers.  Tracks  were  laid  in  parallel  lines  across  the  reservoir 
bottom  from  150  to  200  ft.  apart.  Sand  and  stone  were  hauled 
in  on  these  tracks.  The  sand  was  dumped  in  stock  piles  at  in- 
tervals ;  the  stone  was  shoveled  from  the  cars  directly  into  the 
charging  hopper  and  the  sand  was  delivered  by  wheelbarrows 
to  the  same  hopper.  Four  men  shoveled  the  stone  for  each 
mixer.  To  deliver  the  concrete  from  the  mixer  to  the  work 
required  six  men  with  wheelbarrows.  Two  men  leveled  off 
the  concrete  discharged  by  the  barrows  and  two  other  men 
floated  the  surface  by  means  of  a  straight-edge  spanning  the 
i6-ft.  strips  and  riding  on  the  forms.  By  using  a  wet  but  not 
sloppy  concrete  and  moving  the  straight-edge  back  and  forth 
a  good  surface  was  secured.  The  gang  mixing  ?.nd  placing 
consisted  of  20  men  for  each  mixer  and  18  gangs  laid  ap- 
proximately il/2  acres  per  lo-hour  day.  The  gang  organiza- 
tion and  wages  were  as  follows : 


RESERVOIRS    AND    TANKS.  629 

Item-  Per  10  hours. 

4  men  shoveling  stone  at  $1.50 $  6.00 

2  men  wheeling  sand  at  $1.50 3.00 

2  men  delivering  cement  at  $1.50 3.00 

i  man  dumping  mixer  at  $1.50 1.50 

1  man  tending  engine  and  water  at  $1.50 1.50 

6  men  wheeling  concrete  at  $1.50 9.00 

2  men  spreading  concrete  at  $1.50 3.00 

2  men  leveling  concrete  at  $1.50 3.00 

i  foreman    3.00 

Total  per  day $33.00 

These  costs  do  not  include  the  fraction  of  a  day's  labor  for 
fireman  or  the  cost  of  fuel. 

RESERVOIR  FLOOR,  CANTON,  ILL.— The  following 
costs  are  given  by  Mr.  G.  W.  Chandler  for  lining  the  bottom  of 
a  160  x  8o-ft.  reservoir  with  corners  of  2O-ft.  radius  and  vertical 
brick  sidewalls,  A  1-3^-7^2  crushed  stone  concrete  was 
used ;  it  was  mixed  by  hand  in  batches  of  2.7  cu.  ft.  cement,  9 
cu.  ft.  sand  and  20^  cu.  ft.  stone.  The  sand  and  stone  were 
measured  separately,  the  sand  and  cement  mixed  dry,  then 
shoveled  into  a  pile  with  the  rock,  well  wetted,  shoveled  over 
again  and  then  shoveled  into  wheelbarrows.  The  stone  had  40 
per  cent,  voids  and  the  sand  30  per  cent,  voids.  The  lining 
was  10  ins.  thick  including  a  24-in.  coat  of  1-2*4  mortar  spread 
and  worked  smooth  with  a  trowel.  The  cost  per  cubic  yard 
of  the  lining  in  place  was  as  follows : 

0.856  bbl.  cement  at  $2.50 $2.14 

10.1  bu.  sand  (100  Ibs.  per  bu.)  at  5^4  cts °-5& 

0.857  cu-  yd.  stone  at  $2.17 1.86 

Labor,  mixing  and  placing  at  19  cts.  per  hr 0.80 

Total    $5-38 

RESERVOIR  FLOOR,  PITTSBURG,  PA.— The  follow- 
ing methods  and  costs  of  laying  a  reservoir  floor  are  given 
by  Mr.  Emile  Low,  M.  Am.  Soc.  C.  E.,  for  the  Hiland  Reser- 
voir constructed  at  Pittsburg,  Pa.,  in  1884,  by  contract.  There 
were  7,681  cu.  yds.  of  concrete  in  the  floor  which  was  5  ins. 
thick  and  laid  on  a  clay  puddle  foundation. 


630  CONCRETE  -CONSTRUCTION. 

Natural  cement  costing  $1.35  per  barrel  was  used.  The 
broken  stone  varied  in  weight  from  147  to  152  Ibs.  per  cu.  ft. ; 
it  was  quarried  and  hauled  20  miles  by  rail  and  then  unloaded 
into  small  cars  and  hauled  T/2  mile  to  the  reservoir.  The  cost 
of  the  stone  per  cubic  yard  delivered  was : 

Quarrying,  per  cu.  yd $O-45 

Breaking,  per  cu.  yd 0.35 

Transporting,   per   cu.   yd 0.50 


Total    $1.30 

The  sand  was  'obtained  on  the  site  at  the  cost  of  excavation, 
or  ij4  cts.  per  bushel 

The  method  of  proportioning  and  mixing  the  concrete  was 
as  follows:  Platforms  lox  16  ft.  of  2-in.  plank  were  laid  on 
the  puddle  foundation  and  by  these  were  set  5  x4x  i^-ft. 
boxes  on  legs.  Into  these  boxes  I  bbl.  of  cement  and  2  bbls. 
of  sand  were  emptied  and  thoroughly  mixed  dry,  then  mixed 
with  water  to  a  thin  grout.  Five  barrels  of  stone  were  placed 
on  the  platform  and  thoroughly  wetted ;  the  grout  was  then 
emptied  over  the  stone  and  the  two  turned  over  three  times 
with  shovels.  The  concrete  was  rammed  until  the  mortar 
flushed  to  the  surface.  The  following  costs  cover  various 
periods  as  follows : 

Two  Days  Work  (101  cu.  yds.) :      Total.  Per  cu.  yd. 

27  laborers,  2  days,  at  $1.25 $72.90  $0.7217 

i  foreman,  2  days,  at  $2.50. .....  5.00  0.0495 


Total    $77.90  $0.7712 

One  Month's  Work  (1,302  cu.  yds.) : 

642  days,  laborers,  at  $1.35 $   866.70  $0.6649 

17  days,  water  boy,  at  $0.60.  ....            10.20  0.0078 

22  days,  foreman,  at  $2.50 55-°o  0.0421 


Total  $931-90  $0.7148 


RESERVOIRS    AND    TANKS.  631 

Total  Work  (7,861  cu.  yds.)  : 
Quarrying  stone 

Transporting  stone   o 

Breaking   stone    t  o  ^ 

i  1-3  bbl.  natural  cement !  go 

8  bu.  sand  o  IO 

Water o  O5 

Labor  mixing  and  laying  at  $1.25 o^e 

Incidentals aoc 


Total $4.05 

The  contract  price  was  $6  per  cu.  yd. 


Fig.    286. — Form  for  Constructing  Silo, 

CONSTRUCTING  A  SILO.— The  form  construction 
shown  in  Fig.  286  was  employed  in  building  a  silo  28  ft.  high, 
22  ft.  3  ins.  interior  diameter,  and  having  6-in.  walls.  The 
bottom  of  the  silo  was  made  9  ins.  thick  and  set  2  ft.  below  the 
surface.  The  reinforcement  consisted  of  ten  2^/2  x  3/i6-in. 
rings  spaced  equally  in  the  lower  half  and  of  woven  wire 
fencing  in  the  upper  half.  The  iron  rings  were  hoops  re- 
moved from  an  old  wooden  silo.  The  concrete  was  a  1-6 
mixture  of  Portland  cement  and  sandy  gravel.  Figure  286  is 
a  section  through  the  forms.  There  were  twenty  T-shaped 
posts,  which  extended  perpendicularly  from  the  ground 
to  a  height  of  28  ft.,  being  secured  at  top  and  bottom 
by  a  system  of  guy  ropes  and  posts.  The  rings,  of  which 
there  are  four,  two  inside  and  two  outside,  were  built  of 


632  CONCRETE    CONSTRUCTION. 

weather  boards  with  their  edges  reversed.  Four  thicknesses 
of  board  were  used  in  each  ring.  The  curbing  consisted 
of  2x8-in.  sticks  4  ft.  long.  Wedges  driven  between  the 
vertical  posts  and  the  rings  held  the  latter  in  place.  When 
the  forms  were  to  be  removed  the  wedges  were  knocked  out 
and  the  rings  sprung  enough  to  permit  the  removal  of  the 
curbing.  The  rings  were  then  pushed  up  and  fastened  in  place 
for  another  section.  The  average  rate  of  progress  was  one 
4-ft.  section  per  day.  The  forms  were  filled  in  the  afternoon 
and  moved  up  the  following  forenoon.  Five-foot  sections 
could  have  been  built  just  as  readily. 

The  work  was  all  done  by  farm  laborers  hired  by  the  month 
and  100  man-days  of  such  labor  were  required,  excluding 
seven  days  work  of  a  mason  brushing  and  troweling  the  sur- 
face. The  cost  of  the  work,  not  including  the  old  hoop  iron 
or  the  old  lumber  used  in  forms,  was  as  follows: 

Item.  Total.         Per  cu.  yd. 

Cement $100.00  $2.62 

Gravel  and  sand  35-OO  0.92 

i  2O-rod  roll  of  fencing 5.20  o.oi 

New  lumber 18.00  0.47 

100  days  labor  at  $1.75 I75-OO  4.60 

7  days  mason  troweling  at  $3.50. . .         24.50  0.64 

Total,  38.2  cu.  yds $357-7°  $9.26 

The  external  area  of  the  silo  is  1,950  sq.  ft.,  which  makes 
the  cost  of  brushing  and  troweling  il/±  cts.  per  sq.  ft.  There 
were  about  2,300  ft.  B.  M.  of  lumber  used  in  the  forms,  or 
about  61  ft.  B.  M.  per  cu.  yd.  of  concrete. 

GROINED  ARCH  RESERVOIR  ROOF.— The  following 
data  are  given  by  Mr.  Allen  Hazen  and  Mr.  William  B.  Fuller, 
in  Trans.  Am.  Soc.  C.  E.  1904.  The  concrete  was  mixed  in 
5-ft.  cubical  mixers  in  batches  of  1.6  cu.  yds.  at  the  rate  of  200 
cu.  yds.  per  mixer  day.  One  barrel  of  cement,  580  Ibs.  net, 
assumed  to  be  3.8  cu.  ft.,  was  mixed  with  three  volumes  of 
sand  weighing  90  Ibs.  per  cu.  ft.,  and  five  volumes  of  gravel 
weighing  100  Ibs.  per  cu.  ft.  and  having  40  per  cent,  voids. 
On  the  average  1.26  bbls.  of  cement  were  required  per  cu. 
yd.  The  conveying  plant  consisted  of  two  trestles  (each  900 


RESERVOIRS    AND    TANKS.  633 

ft.  long)  730  ft.  apart,  supporting  four  cableways.  The  cables 
were  attached  to  carriages,  which  ran  on  I-beams  on  the  top 
of  the  trestles.  Rope  drives  were  used  to  shift  the  cableways 
along  the  trestle.  Three-ton  loads  were  handled  in  each  skip. 
The  installation  of  this  plant  was  slow,  and  its  carrying  capac- 
ity was  less  than  expected.  It  was  found  best  to  deliver  the 
skips  of  concrete  to  the  cableway  on  small  railway  track, 
although  the  original  plan  had  been  to  move  the  cableways 
horizontally  along  the  trestle  at  the  same  time  that  the  skip 
was  traveling. 

The  cost  of  mixing  and  placing  the  concrete  was  as  follows : 

Per  cu.  yd. 

Measuring,  mixing  and  loading $0.20 

Transporting  by  rail  and  cables 0.12 

Laying  and  tamping  floors  and  walls  including  setting 
forms 0.22 

Total  $0.54 

The  cost  of  laying  and  tamping  the  concrete  on  the  vaulting 
was  14  cts.  per  cu.  yd.  The  vaulting  is  a  groined  arch  6  ins. 
thick  at  the  crown  and  2l/2  ft.  thick  at  the  piers. 

The  lumber  of  the  centering  for  the  vaulting  was  spruce 
for  the  ribs  and  posts,  and  i-in.  hemlock  for  the  lagging. 
The  centering  was  all  cut  by  machinery,  the  ribs  put  to- 
gether to  a  template,  and  the  lagging  sawed  to  proper  bevels 
and  lengths.  The  centers  were  made  so  that  they  could  be 
taken  down  in  sections  and  used  again.  The  cost  of  center- 
ing was  as  follows: 

Labor  on  centers  covering  62,560  sq.  ft. 

Foreman,  435  hrs.  at  35  cts $    i52-25 

Carpenters,  4,873  hrs.  at  22^  cts 1,096.42 

Laborers,  3,447  hrs.  at  15  cts : S17-°S 

Painters,  577  hrs.  at  15  cts 86.55 

Teaming,  324  hrs.  at  40  cts 121.60 


Total  labor  building  centers,  313  M.  at  $6.37.  .$1,973-87 
Materials  for  centers  covering  62,560  sq.  ft. 


634 


CONCRETE    CONSTRUCTION. 


313,000  ft.  B.  M.  lumber,  at  $18.20 $5,700.00 

3,700  Ibs.  nails,  at  3  cts in.oo 

8  bbls.  tar,  at  $3 24.00 


Total    $5,835-oo 

These  centers  covered  two  niters,  each  having  an  area  of 
121  1-3x258  ft.  There  were  six  more  filters  of  the  same  size, 
for  which  the  same  centers  were  used.  The  cost  of  taking 
down,  moving  and  putting  up  these  centers  (313  M.)  three 
times  was  as  follows : 


Elevation. 
Fig.    287.— Forms    for    Constructing    Grain    Elevator   Bins. 

Foreman,  2,359  nrs-  at  35  cts $   825.65 

Carpenters,  12,766  hrs.  at  22^  cts 2,872.35 

Laborers,  24,062  hrs.  at  15  cts 3,609.30 

Team,  430  hrs.  at  40  cts 172.00 

3,000  ft.  B.  M.  lumber,  at  $20 60.00 

3,000  Ibs.  nails,  at  3  cts 90.00 


Total  cost  of  moving  centers  to  cover  196,660 

sq.  ft $7,629.30 

The  cost  of  moving  the  centers  each  time  was  $8.10  per  M., 
showing  that  they  were  practically  rebuilt;  for  the  first 
building  of  the  centers,  as  above  shown,  cost  only  $6.37  per  M. 
In  other  words,  the  centers  were  not  designed  so  as  to  be 
moved  in  sections  as  they  should  have  been.  Although  the 
centers  were  used  four  times  in  all,  the  lumber  was  in  fit 
condition  for  further  use.  The  cost  of  the  labor  and  lumber 


RESERVOIRS    AND    TANKS.  635 

for  the  building  and  moving  of  these  centers  for  the  8  filter 
beds,  having  a  total  area  of  259,220  sq.  ft.,  was  $15438,  or 
6  cts.  per  sq.  ft. 

GRAIN  ELEVATOR  BINS.— In  constructing  cylindrical 
bins  30  ft.  in  diameter  and  90  ft.  high  for  a  grain  elevator  the 
forms  shown  by  Fig.  287  were  used.  For  the  inside  wall  a 
complete  ring  of  lagging  4  ft.  high  nailed  to  circular  horizontal 
ribs  of  2  x  8-in.  planks  was  used.  For  the  outside  wall  two, 
three  or  four  segments  fitting  the  clear  spaces  between  adjoin- 
ing tanks  were  used,  these  panel  segments  being  also  4  ft. 
high.  The  inside  and  outside  rings  were  held  together  by 
yokes  constructed  as  shown,  and  bolted  to  the  inner  and 
outer  ribs.  A  staging  built  up  inside  the  tank  carried  jack 
screws,  on  which  were  seated  the  inner  legs  of  the  yokes. 


CHAPTER  XXIII. 

METHODS  AND   COST  OF   CONSTRUCTING  ORNA- 
MENTAL WORK. 

The  safest  rule  for  ornamental  work  is  to  leave  its  construc- 
tion to  those  who  make  a  specialty  of  such  work.  This  is  per- 
fectly practicable  in  most  concrete  structures  having  orna- 
ment. Bridge  railings  can  be  and  usually  are  made  up  of 
separately  molded  posts,  balusters,  bases  and  rail.  Orna- 
mental columns  in  building  work,  key-stones,  medallions, 
brackets,  dentils,  rosettes,  and  cornice  courses  can  be  similarly 
molded  and  placed  in  the  structure  as  the  monolithic  work 
reaches  the  proper  points.  The  general  constructor,  there- 
fore, can  readily  delegate  these  special  parts  of  his  concrete 
bridge  or  building  to  specialists  at  frequently  less  cost  to 
himself  and  nearly  always  with  greater  certainty  of  good  re- 
sults than  if  he  installed  molds  and  organized  a  trained  gang 
for  doing  the  work. 

Good  concrete  ornament  is  not  alone  a  matter  of  good 
design.  It  is  also  a  matter  of  skilled  construction.  Nearly 
anyone  can  mold  an  ornament,  but  few  can  mold  an  ornament 
which  is  durable.  To  produce  clean,  sharp  lines  and  arises 
which  will  endure,  the  molder  must  have  special  knowledge 
and  familiarity  with  the  action  of  cement  and  of  concrete  mix- 
tures, both  in  molding  and  on  exposure  to  the  elements.  This 
is  knowledge  that  the  general  concrete  worker  rarely  pos- 
sesses but  which  the  ornament  molder  does  possess  if  he 
knows  his  business.  Special  work  is  always  best  left  to  the 
specialist. 

While  the  more  intricate  ornamental  work  is  best  done  by 
sub-contract,  so  far  at  least  as  the  actual  molding  of  the 
ornaments  is  concerned,  there  is  a  large  amount  of  simple 
paneling  and  molding  which  the  general  practitioner  not  only 
can  do  but  must  do.  Knowledge  of  the  best  methods  of  doing 


ORNAMENTAL    WORK.  637 

such  work  is  essential  and  it  is  also  essential  that  the  con- 
structor should  know  in  a  general  way  of  the  special  methods 
of  molding  intricate  ornaments. 

SEPARATELY  MOLDED  ORNAMENTS.— The  cement 
for  ornamental  work  must  be  strong  and  absolutely  sound. 
Where  an  especially  light  color  is  wished  a  light  colored 
cement  is  desirable.  So  called  white  cements  are  now  being 
manufactured.  Lafarge  cement,  a  light  colored,  non-staining 
cement  made  in  France,  gives  excellent  results.  Of  Ameri- 
can cements,  Vulcanite  cement  has  a  light  color,  and  next  to 
it  in  this  respect  comes  Whitehall  cement.  A  light  colored 
ornament  can,  however,  be  secured  with  any  cement  by  using 
white  sand  or  marble  or  other  white  stone  screenings.  Some 
authorities  advocate  this  method  of  securing  light  colored 
blocks  as  always  cheaper  and  usually  superior  to  the  use  of 
special  cements.  The  choice  between  the  two  methods  will  be 
governed  by  the  results  sought ;  where  as  nearly  as  possible 
a  pure  white  is  desired  it  stands  to  reason  that  a  white  or 
nearly  white  cement  will  give  the  better  results. 

In  the  matter  of  sand  and  aggregate  for  ornamental  work, 
the  kinds  used  will  ordinarily  be  the  kinds  that  are  available. 
They  must  conform  in  quality  to  the  standard  requirements 
of  such  materials  for  concrete  work.  Where  special  colors  or 
tints  are  wanted  they  can  be  secured  by  using  for  sand  and 
aggregate  screenings  from  stones  of  the  required  color.  This 
is  in  all  respects  the  best  method  of  securing  colored  blocks, 
as  the  color  will  not  fade  and  the  concrete  is  not  weakened. 
A  great  variety  of  pigments  are  made  for  coloring  concrete ; 
these  colors  all  fade  in  time,  and  with  few  exceptions  they 
all  weaken  the  concrete.  The  mixtures  used  in  ornamental 
work  will  depend  upon  the  detail  of  the  ornament  and  upon 
whether  color  is  or  is  not  required.  Generally  a  rich  mixture 
of  cement  and  sand  or  fine  stone  screenings  will  be  used  for 
the  surface  and  will  be  backed  with  the  ordinary  concrete 
mixture.  A  surface  mixture  of  fine  material  is  necessary 
where  clear,  sharp  lines  and  edges  or  corners  are  demanded. 

The  molds  used  for  ornament  are  wooden  molds,  iron 
molds,  sand  molds  and  plaster  of  Paris  and  special  molds. 


638  CONCRETE    CONSTRUCTION. 

Each  kind  has  its  field  of  usefulness,  and  its  advantages  over 
the  others.  They  will  be  considered  briefly  in  the  order 
named. 

Wooden  Molds. — Wooden  molds  are  perhaps  the  best  for 
general  work  where  plain  shapes  and  not  too  delicate  orna- 
mentation are  wanted.  They  give  the  best  results  only  with 
a  quite  dry  and  rather  coarse  grained  surface  mixture.  If  a 
wet  mixture  is  used  such  water  as  flushes  to  the  surface  can- 
not escape  and  small  pits  and  holes  are  formed,  which  neces- 
sitates grout  or  other  finishing.  The  following  are  examples 
of  wooden  mold  work: 

In  constructing  a  five-span  reinforced  concrete  arch  bridge 
at  Grand  Rapids,  Mich.,  in  1904,  the  railings  and  ornamental 
parts  of  the  bridge,  such  as  keystones,  brackets,  consols,  den- 
tiles  and  panels,  were  cast  in  molds  and  set  in  place  much  as 
cut  stone  would  be.  Special  molds  were  employed  for  each 
of  these  different  shapes.  These  molds  were  plastered  with 
an  earth  damp  mortar  composed  of  i  part  cement  and  2l/2 
parts  fine  sand,  which  was  followed  up  with  a  backing  of  wet 
concrete  composed  of  I  part  cement,  2  parts  sand  and  3 
parts  broken  stone  passing  a  24-in.  ring.  The  facing  mortar 
was  made  il/2  ins.  thick.  The  castings  cannot  be  told  from 
dressed  stone  at  a  few  feet  distance. 

The  part  elevation  and  sections  in  the  drawings  of  Fig. 
288  show  the  arrangement  of  the  various  castings  to  form  the 
completed  railing,  coping,  etc.  To  specify,  A  is  the  arch  ring, 
B  the  brackets,  C  the  coping,  and  D,  E,  F,  respectively,  the 
base,  balusters  and  rail  of  the  bridge  railing.  The  blocks  G 
and  H  show  the  keystone  and  railing  post.  The  forms  or 
molds  for  each  of  these  parts  are  shown  by  the  other  drawings 
of  Fig.  288.  A  description  of  each  of  these  forms  follows : 

The  keystones  were  molded  in  wooden  forms,  consisting  of 
one  piece,  a,  forming  the  top  and  front;  of  two  side  pieces,  f, 
of  a  bottom  consisting  of  two  parts,  b  and  c ;  and  of  a  back 
piece,  g.  The  back  and  side  pieces  are  stiffened  with  2  x  3^- 
in.  pieces,  and  the  front,  sides  and  back  are  held  together  by 
yokes  or  clamps.  The  front  of  the  mold  was  the  only  portion 
calling  for  particular  work,  and  this  was  made  of  boards  lam- 
inated together. 


ORNAMENTAL    WORK. 


639 


The  bracket  molds  consisted  of  two  side  pieces  provided 
with  grooves  for  receiving  the  front  and  back  pieces,  and  with 
slots  for  tie  rods  clamping  the  whole  mold  together.  It  will 
be  noted  also  that  the  side  pieces  had  nailed  to  them  inside  a 
beveled  strip  to  form  a  groove  in  each  side  of  the  cast  block. 
The  purpose  of  this  groove  was  to  provide  a  bond  to  hold  the 
bracket  more  firmly  in  the  adjoining  concrete  of  the  wall.  The 
bottom  of  the  mold  was  formed  by  a  2-in.  plank,  and  when 
the  concrete  had  been  tamped  in  place  the  forms  were  re- 
moved, and  the  bracket  was  left  on  the  bottom  to  set.  It  may 


4i'C.G. 
Moulding...^  .lop  Tmishetf  mth  Trmttf 


Mold     for    "E* 

Fig.    288. — Molds   for  Railings   and   Ornaments   for  Concrete  Arch   Bridge. 

be  noted  here  that  a  goodly  number  of  the  brackets  showed  a 
crack  at  the  joint  marked  x  caused  by  tamping  at  the  point 
y.  In  construction  the  bracket  castings  were  set  at  proper 
intervals  on  the  spandrel  walls,  which  had  been  completed  up 
to  the  level  of  the  line  X  Y.  The  coping  course  was  then 
built  up  around  the  bracket  blocks  to  the  level  of  the  bottom 
of  the  railing  base. 

The  mold  or  form  for  the  coping  course  was  designed  to 
build  the  coping  in  successive  sections,  and  was  built  up 
around  the  bracket  blocks,  and  supported  from  the  centers  as 
shown  by  the  drawings.  To  form  the  expansion  joints  in  the 


640  CONCRETE    CONSTRUCTION. 

coping  course  there  were  inserted  across  the  mold  at  proper 
intervals  a  short  iron  plate  l/^  in.  thick,  cut  to  fit.  The  cut- 
ting of  this  plate  was  found  to  be  a  slow  operation. 

The  forms  for  the  base  of  the  railing  (Section  D)  consisted 
of  i^-in.  stock  for  the  sides,  and  24-in.  stock  for  the  slopes. 
They  extended  across  the  arch,  and  were  held  together  by  a 
very  simple  though  very  efficient  clamp.  This  consisted  of 
two  2  x  3  x  33-in.  pieces  nailed  to  a  2x3x17-^.  piece  by 
means  of  galvanized  iron  strips.  About  half-way  down  the 
long  pieces,  a  l/2-m.  rod  was  run  through,  and  secured  up 
against  blocks,  h,  placed  about  56  ins.  apart.  These  blocks 
were  removed  as  the  concrete  was  put  in  place.  It  will  be 
noticed  from  the  cross-section  of  the  railing  that  the  balusters 
are  set  into  sockets  formed  in  the  top  of  the  base  course. 
These  sockets,  were  formed  by  means  of  the  mold  shown  at 
W  and  Z. 

In  casting  the  balusters,  Section  (£),  a  ^6 -in.  cast  iron  mold, 
consisting  of  four  iron  sides  and  an  iron  top,  was  used.  Orig- 
inally there  were  two  end  plates  of  iron,  but  it  was  found 
more  convenient  to  have  the  bottom  one  of  wood  and  allow 
the  cast  spindle  to  stand  and  set.  The  mold  was  held  to- 
gether by  l/2-'m.  bolts.  It  would  have  been  more  practical 
to  have  had  the  side  casting  composed  of  two  parts. 

The  form  for  the  railing  is  built  up  around  the  tops  of 
the  spindles.  The  bottom  piece  is  I  x  9  ins.,  to  which  4^4-in. 
ogee  molding  is  nailed.  The  sides  are  of  i-in.  stock,  and  are 
clamped  together.  The  top  is  finished  off  with  a  trowel. 

The  mold  for  the  posts  is  made  in  four  parts,  which  fit  to- 
gether at  the  top  and  bottom  by  a  bevel  joint,  as  shown  in  the 
one-fourth  section.  The  broad  sides  rest  against  the  narrow 
ones,  and  are  held  against  the  same  by  means  of  y2-in.  rods 
running  through  2  x3-in.  stock;  2-in.  projections  of  the  broad 
sides  facilitate  the  removal  of  the  form  from  the  completed 
post. 

In  constructing  a  concrete  *acade  for  a  plate  girder  bridge 
at  St.  Louis,  Mo.,  the  railing  above  the  base  was  constructed 
of  separately  molded  blocks  as  follows :  The  balusters  were 
cast  in  plaster  molds.  To  make  these  molds  a  box  square  in 


ORNAMENTAL    WORK. 


641 


plan  and  the  height  of  the  baluster  was  constructed  of  wood 
and  cut  vertically  into  three  sections.  The  inside  lateral  di- 
mensions of  this  box  were  made  6  ins.  greater  than  the 
largest  dimension  of  the  baluster.  A  full  size  wooden  pattern 
of  the  baluster  was  set  up  and  the  three  sections  of  the  box 


Btr/usfers 


Mold 


Fig.    289.-Molds    for    Ornamental    Railing    Posts    for   Concrete    Facade    for 

were  set  around  it.  Sheets  of  thin  galvanized  metal,  with 
their  inner  edges  cut  to  conform  to  the  curves  of  the  baluster, 
were  inserted  in  the  joints  of  the  assembled  box  so  as  to  di- 
vide the  vacant  space  between  the  pattern  and  the  box  into 
vertical  sections.  A  mixture  of  i  part  Portland  cement  and 


642 


CONCRETE    CONSTRUCTION. 


i  part  plaster  of  Paris,  made  wet,  was  then  poured  around 
the  pattern  until  the  box  was  filled.  When  this  mixture  had 
become  hard,  the  box  was  taken  down,  leaving-  a  plaster  arid 
cement  casing  separated  into  three  parts  by  the  sheets  of  gal- 


zzn 


Horizontal      Section. 


» 


CN6.NEW4. 

Side    Elevation. 
Fig.    290.— Railing    for    Arch    Bridge. 


Vertical 
Section. 


vanized  metal.  This  casing  was  separated  from  the  pattern 
and  given  a  coat  of  shellac  on  the  inside.  Four  or  five  molds 
of  this  description  were  cast.  To  cast  a  baluster,  the  sec- 
tions were  assembled  and  a  ^2-in.  corrugated  bar  was  set 


S£  _____  H 
—I'  It'  -  -*&  --  ?/£•  ---  N 


Fig.    291.—  Form    for    Lattice    Panels    Shown   by   Fig.    290. 

vertically  in  the  center.  A  mixture  of  I  part  Portland  ce- 
ment and  3  parts  sand  was  then  poured  into  the  mold  and 
allowed  to  harden.  The  molds  for  the  urns  on  the  railing  post 
and  the  balls  on  the  end  posts  were  made  in  exactly  the  same 


ORNAMENTAL    WORK.  643 

manner  as  the  baluster  molds.     The  construction  of  the  rail- 
ing posts  is  shown  by  the  drawings  of.  Fig.  289.     Referring 
first  to  the  end  posts,  it  will  be  seen  that  they  were  molded  in 
place  in  seven  sections  marked  A,  B,  C,  D,  E,  F  and  G.     The 
construction  of  the  mold  for  each  section  is  shown  by  the  cor- 
respondingly  lettered   detail.      The    intermediate    posts   were 
built    up    of    the    separately  molded    pieces  I,  K  and  H.     The 
costs  of  molding  the  several   parts  were:   Balusters,  60  cts. 
each ;  hand  rail,  40  cts.  per  lin.  ft.  The  six  intermediate  posts 
cost  $12  each,  and  the  four  end  or  newel  posts  cost  $75  each. 
In  constructing  the  72-ft.  span-ribbed  arch  bridge  over  Deer 
Park  Gorge,  near  La  Salle,  111.,  a  hand  railing  of  the  design 
shown  by  Fig.  290,  was  used.    In  constructing  this  railing,  the 
posts  were  molded   in   place, ,  but  the  open  work  panels  be- 
tween posts  .and  the  hand  rail  proper  were  molded  separately 


Z»x4'-?0"apart 


-—  7" 


Fig.    292.— Form    for    Hand    Rail    Shown    by    Fig.    290. 

and  set  in  place  between  the  posts  as  indicated.  For  molding 
the  panels  a  number  of  boxes  constructed  as  shown  by  Fig. 
291,  were  used.  These  were  simple  rectangular  boxes  on  the 
bottom  boards  of  which  were  nailed  blocks  of  the  proper 
shape  and  in  the  proper  position  to  form  the  openings  in  the 
railing.  The  bottom  of  the  form  was  first  plastered  with 
mortar,  then  the  concrete  was  filled  in  and  plastered  on  top. 
As  soon  as  the  concrete  had  begun  to  set  the  blocks  were 
removed  so  that  final  setting  could  take  place  without  danger 
of  cracking.  When  the  concrete  had  set  so  that  the  panel 
could  be  safely  handled,  it  was  removed  from  the  form  and 
stored  until  wanted.  The  hand  rail  for  each  side  was  molded 
in  two  pieces  in  forms  constructed  as  shown  by  Fig.  292. 
The  total  cost  of  the  railing  in  place  was  about  $2  per  lineal 


644  CONCRETE    CONSTRUCTION. 

foot.    The  concrete  was  a  1-2-4  mixture  of  screenings  and  %- 
in.  broken  stone. 

Iron  Molds. — Iron  molds  have  the  same  disadvantages  as 
wooden  molds  in  the  use  of  wet  mixtures.  They  can  be  made 
to  mold  more  intricate  ornaments,  and  in  the  matter  of  dura- 
bility, are,  of  course,  far  superior  to  wood.  Iron  molds  can  be 
ordered  cast  to  pattern  in  any  well  equipped  foundry.  Many 
firms  making  block  machines  also  make  standard  column, 
baluster,  ball  and  base,  cornice,  and  base  molds  of  various 
sizes  and  patterns.  These  molds  are  made  in  two,  three  or 
more  sections  which  can  be  quickly  locked  together  and  taken 
apart.  A  column  mold,  for  example,  will  consist  of  a  mold 
for  the  base,  another  for  the  shaft,  and  a  third  for  the  capitol. 
each  in  collapsible  sections.  Where  the  pattern  of  the  shaft 
changes  in  its  height,  two  shaft  molds  are  commonly  used,  one 
for  each  pattern.  Prices  of  iron  molds  are  subject  to  varia- 
tion, but  the  following  are  representative  figures :  Plain  balus- 
ter molds  14  to  18  ins.  high,  $7.50  to  $10  each ;  fluted  square 
balusters,  14  to  18  ins.  high,  $10,  each ;  ball  and  base,  10  to 
i8-in.  balls,  $15  to  $25  each;  fluted  Grecian  column,  base, 
capitol  and  one  shaft  molds,  $30;  Renaissance  column,  base, 
capitol  and  two  shaft  molds,  $45. 

Sand  Molding.— Molding  concrete  ornaments  in  sand  is  in 
all  respects  like  molding  iron  castings  in  a  foundry.  Sand 
molding  gives  perhaps  the  handsomest  ornament  of  any  kind 
of  molding  process,  the  surface  texture  and  detail  of  the  block 
being  especially  fine.  It  is,  however,  a  more  expensive  process 
than  molding  in  wooden  or  iron  molds,  since  a  separate  mold 
must  be  made  for  each  piece  molded.  The  process  was  first 
employed  and  patented  in  1899,  by  Mr.  C.  W.  Stevens,  of  Har- 
vey, 111.,  and  for  this  reason  it  is  often  called  the  Stevens 
process.  Sand  molded  ornaments  and  blocks  are  made  by  a 
number  of  firms  to  order  to  any  pattern.  The  process  as  em- 
ployed at  the  works  of  the  Roman  Stone  Co.,  of  Toronto,  Ont., 
is  as  follows:  The  stone  employed  for  aggregate,  is  a  hard, 
coarse,  crystalline  limestone  of  a  light  grey  color,  being  prac- 
tically 97  per  cent,  calcium  carbonate,  with  a  small  percentage 
of  iron,  aluminia  and  magnesia.  Nothing  but  carefully  se- 
lected quarry  clippings  are  used  and  these  are  crushed  and 


ORNAMENTAL    WORK.  645 

ground  at  the  factory  and  carefully  screened  into  three  sizes, 
the  largest  about  the  size  of  a  kernel  of  corn.  Daily  granulo- 
metric  tests  are  made  of  the  crusher  output  to  regulate  the 
amount  of  each  size  got  from  the  machines.  It  has  been 
found  that  next  in  importance  to  properly  graded  aggregates 
is  the  gaging  of  the  amount  of  water  used  in  the  mixture. 
This  is  done  by  an  automatically  filled  tank  into  which  lead 
both  hot  and  cold  water  and  in  which  is  fixed  a  thermometer 
to  properly  regulate  the  temperature.  In  gaging  the  mix 
about  20%  of  water  is  used,  but  of  course  when  the  cast  is 
made  the  surplus  is  immediately  drawn  off  into  the  sand, 
where  it  is  retained  and  serves  as  a  wet  blanket  to  protect  the 
cast  and  supply  it  with  the  proper  amount  of  water  during 
crystallization.  Experiments  seem  to  indicate  that  about  15% 
by  weight  gives  the  greatest  amount  of  strength  of  mortar  at 
the  age  of  six  months,  while,  giving  less  strength  at  shorter 
time  tests  than  mortar  gaged  with  a  smaller  percentage  of 
water. 

The  method  of  handling  the  mix  and  casting  is  quite  sim- 
ple and  almost  identical  with  the  practice  in  iron  foundries. 
The  mixture  is  made  in  a  batch  mixer  to  about  the  same  con- 
sistency as  molasses,  from  which  it  is  poured  into  a  mechanical 
agitator  and  carried  about  the  foundry  by  a  traveling  crane. 
This  agitator  is  so  constructed  that  it  keeps  the  materials  in 
motion  constantly  and  prevents  their  segregation.  In  each 
cast  is  inserted  the  proper  reinforcing  rods,  lifting  hooks  and 
tie  rods,  and  the  casts  are  allowed  to  remain  for  a  proper 
period  in  the  wet  sand  after  they  are  poured ;  they  are  then 
taken  to  the  seasoning  room  which  is  kept  at  as  constant  a 
temperature  as  it  is  practical  to  maintain.  Each  cast  is 
marked  with  the  number  which  determines  its  location  in  the 
building  and  the  date  it  was  cast,  and  it  is  then  kept  in  the 
storage  shed  a  fixed  time  before  shipping. 

Records  are  kept  of  each  cast  made  and  the  company  is  able 
to  get,  as  in  mills  rolling  structural  steel,  the  exact  number 
and  location  of  all  casts  made  from  the  same  mix.  Careful 
records  are  always  kept  of  the  tests  of  cement  and  material, 
and  test  cubes  are  made  from  each  consignment  of  cement 
so  tested ;  in  this  way  all  danger  of  defective  stone  through  in- 


646  CONCRETE    CONSTRUCTION. 

ferior  cement  is  eliminated.  The  patterns  used  in  making 
the  molds  and  the  method  of  molding-  are  quite  similar  to  or- 
dinary iron  foundry  practice  except  that  the  sand  used  is  of 
special  nature.  The  finish  of  the  stone  is  generally  tooled 
finish  molded  in  the  sand,  the  different  textures  of  natural 
stone  being  produced  by  the  veneering  of  the  pattern  with 
thin  strips  of  wood  which  are  run  through  a  machine  pro- 
ducing the  different  finishes.  Each  stone  is  provided  with 
setting  hooks  cast  in  the  blocks  which  take  the  place  of  the 
ordinary  lewis  holes  used  in  cut  stone. 

Plaster  Molds. — Plaster  of  Paris  molds  are  made  from  clay, 
gelatin  or  other  patterns  in  the  usual  manner  adopted  by 
sculptors.  They  are  particularly  adapted  to  fine  line  and 
under  cut  ornaments.  The  concrete  is  poured  into  the  plaster 
mold  and  after  the  cement  has  become  hard,  the  plaster  is 
broken  or  chiseled  away,  leaving  the  concrete  exposed.  Two 
examples  of  excellent  work  in  intricate  concrete  ornaments 
are  furnished  by  the  power  house  for  the  Sanitary  District 
of  Chicago,  and  by  the  State  Normal  School  building,  at 
Kearney,  Neb.  In  the  power  house,  the  ornamental  work 
consisted  of  molded  courses,  cornice  work ;  and  particularly 
of  heavy  capitols  for  pilasters.  These  capitols  were  very 
heavy,  being  7J^  ft.  long  and  of  the  Ionic  design.  These  were 
made  from  plaster  molds;  made  so  as  to  be  taken  apart  or 
knocked  down  and  to  release  in  this  way,  perfectly.  There 
were  also  scrolls,  keystones  and  arches  in  curved  design  over 
all  of  the  40  windows.  None  of  this  ornament  was  true  under 
cut  work.-  In  building  the  Normal  School  building,  Cor- 
inthian capitols,  in  quarters,  halves,  corners  and  full  rounds 
were  made  in  plaster  molds.  There  were  some  30  of  these 
capitols.  They  were  made  in  solid  plaster  molds ;  the  molds 
having  been  cast  in  gelatine  molds,  one  for  each  capitol.  Into 
these,  the  concrete  was  tamped,  made  very  wet,  and  after 
the  concrete  had  hardened,  the  plaster  cast  was  chiseled  away. 
This  was  very  easily  accomplished.  These  capitols  were  true 
Corinthians,  having  all  the  floriation  and  under-cut  usually 
seen  in  such  capitols. 


ORNAMENTAL    WORK. 


647 


ORNAMENTS  MOLDED  IN  PLACE.— Molding  orna- 
ments in  place  is  usually,  and  generally  should  be,  confined 
to  belt  courses,  cornices,  copings  and  plain  panels.  Relief 
work,  like  keystones,  scrolls  or  rosettes,  can  be  molded  in 
place  if  desired,  by  setting  plaster  molds  in  the  wooden  forms 

at  the  proper  points.  This 
method  is  often  advantageous 
in  bridge  work,  where  compar- 
atively few  ornaments  are  re- 
quired, such  as  keystones. 

The  construction  of  forms 
for  ornamental  work  in  place 
is  best  described  by  taking  spe- 
cific examples.  Figure  293, 
shows  the  face  form  for  the 
arch  ring,  spandrel  wall  and 
cornice  or  coping  course  of  the 
Big  Muddy  River  Bridge  on 
the  Illinois  Central  R.  R,  The 
secfion  is  taken  near  the  crown 
of  the  arch.  The  lagging  only 
is  shown  ;  this  was,  of  course, 
backed  with  studding.  The 
point  to  be  noted  in  this  form 
is  the  avoidance  of  any  ap- 
proach to  under  cut  work; 
there  are,  in  fact,  very  few 
straight  cut  details.  This 
brings  up  a  point  that  must  be 
carefully  watched  if  trouble  is 
to  be  avoided,  namely,  the  con- 
struction of  the  form  work  in 
sections  which  can  be  removed 
without  fracturing  the  ornament.  To  illustrate  by  an  as- 
sumed example,  supposing  it  is  required  to  mold  the 
wall  and  cornice  shown  by  Fig.  294.  It  is  clear  that  if  the 
backing  studs  are  in  single  pieces,  notched  .as  shown,  the 
forms  cannot  be  removed  without  fracturing  at  least  the  cor- 
ner A.  If  the  studs  and  lagging  be  constructed  in  two  parts, 
separated  along  the  line  a  b,  the  form  is  possible  of  removal  if 


EN6. 
NEWS. 


Fig.  293.— Spandrel  Wall  Mold 
for  Arch  Bridge. 


648 


CONCRETE    CONSTRUCTION. 


great  care  is  used  without  damage  to  the  concrete.  The  con- 
struction shown  by  this  sketch  does  not  greatly  exaggerate 
matters.  Figure  295  shows  a  wall  form  that  has  been  given 
several  times  as  a  presumably  good  example  in  which,  as  will 
be  seen  it  is  impossible  to  remove  the  board  a,  without  break- 
ing the  concrete  even  if  the  narrow  face  were  not  broken  by 
the  swelling  of  the  lumber  before  ever  it  became  time  to  take 
down  the  forms. 

This  matter  of  making  provision  for  the  swelling  of  the 
forms  is  another  point  to  be  watched.  Referring  again  to 
Fig.  294  it  will  be  seen  that  the  swelling  of  the  lagging,  even 


Fig.    294. — Diagram   Illustrating 
Details   of   Mold   Construction. 


Fig.    295. — Example    of   Poor 
Wall    Form   Construction. 


if  the  cornice  instead  of  being  under  cut  at  A  were  straight 
cut  on  the  line  c  d,  is  liable  so  to  crowd  the  lagging  into  the 
corner  A  and  B  that  the  concrete  is  cracked  along  the  lines 
e  f  or  g  h.  A  suggested  remedy  for  this  danger  is  shown  by 
Fig.  296.  At  a  distance  of  every  3  or  4  ft.  insert  a  narrow  piece 
of  lagging  a  and  behind  these  lagging  strips  cut  notches  b  in 
the  studs.  When  the  concrete  has  got  its  initial  set  pull  back 
the  lagging  strip  a  into  the  notches  bf  leaving  an  open  joint  to 
provide  for  expansion  due  to  swelling. 


ORNAMENTAL    WORK. 


649 


.-  In  constructing  a  concrete  facade  for  a  plate  girder  bridge  at 
St.  Louis,  Mo.,  the  form  shown  by  Fig.  297  was  used.     The 


/'Pint 


Fig.    296.— Notched   Studding  for 

Removal   of   Lagging   Board   to 

Permit    Swelling. 


Concrete  la/etto'thvltne     , 

one/ Mowfd  fo  Set  Wire  Support  B»». 

to  Bracket 

Fig.  297. — Form  for  Concrete  Facade 
Shown  by  Fig.  298. 


CNG. 
NCW5. 


Fig.    298.— Concrete   Facade    for    Plate    Girder    Bridge. 

completed  facade  is  shown  by  Fig.  298.    The  ceiling  slab  was 
first  built  and  allowed  to  set  and  then  the  forms  were  erected 


650 


CONCRETE    CONSTRUCTION. 


for  the  frieze  and  coping.    After  these  were  molded  the  forms 
were  continued  upward  as  shown  for  the  base  of  the  railing. 


Section  A-B  Section  C'O        Section  £-F      Section  G-M 


Fig.  299.— Forms  for  Curved  Concrete  Abutments. 

Above  this  point  the  several  parts  were  separately  molded  as 
shown   by   Fig.    285    previously   described.      Molded    in    this 


llpiiiii; 

^•y  y';'fy.  Concrete  \-,  V  -^'y.  ij: 


Jfl 

Fig.  300.— Cornice  Form.  Fig.    301.— Method   of   Supporting 

Cornice   Form  Shown   by   Fig.   300. 

manner  the  ceiling  cost  25   cts.  per  sq.  ft.;    the  frieze   and 
coping  cost  $2  per  lin.  ft.,  and  the  railing  base  cost  45  cts.  per 


ORNAMENTAL    WORK. 


651 


lin.  ft.  In  constructing  the  concrete  abutments  of  this  same 
structure  use  was  made  of  the  forms  shown  by  Fig.  299. 
These  abutments  had  curved  wing  walls  and  for  molding  these 
girts  cut  to  the  radii  of  the  curves  were  fastened  to  the  studs 
and  vertical  lagging  was  nailed  to  the  girts.  All  the  lagging 
was  tongue  and  groove  stuff. 

In  constructing  an  open  spandrel  arch  bridge  at  St.  Paul, 
Minn.,  the  cornice  form  shown  by  Fig.  300,  supported  as 
shown  by  Fig.  301,  was  used.  The  particular  feature  of  this 
form  was  the  use  of  a  lath  and  plaster  lining  to  the  lagging. 


ENO. 
NEW*. 


Fig.    302.— Cornice    and    Balustrade    for    Arch    Bridge. 

This  lining  was  used  for  all  exposed  surfaces  of  the  bridge. 
So  called  patent  lath  consisting  of  boards  with  parallel  dove- 
tail grooves  and  ridges  was  used.  This  was  plastered  with  ce- 
ment mortar  and  the  concrete  was  deposited  directly  against 
the  plaster  after  smearing  the  plaster  surface  with  boiled  lin- 
seed oil.  This  lining  is  stated  to  have  given  an  excellent  sur- 
face finish  to  the  concrete.  It  cost  55  cts.  per  sq.  ft.  for  materi- 
als and  labor.  A  section  of  the  balustrade  and  cornice  is  shown 
by  Pig.  302.  The  posts,  balusters  and  railing  were  molded 
separately.  The  balusters  were  molded  in  zinc  molds.  At 


652  CONCRETE    CONSTRUCTION. 

first  some  trouble  was  had  in  getting  good  casts  on  account 
of  air  pockets.  This  was  largely  done  away  with  by  filling  the 
mold  as  compactly  as  possible  and  then  driving  a  J^-in.  iron 
rod  through  the  center  vertically;  this  rod  crowded  the  con- 
crete into  all  parts  of  the  mold  and  also  served  to  strengthen 
the  baluster.  The  baluster  molds  were  made  in  two  parts ; 
this  proved  a  mistake — three  parts  would  have  been  better. 


CHAPTER  XXIV. 


MISCELLANEOUS    DATA   ON    MATERIALS,   MA- 
CHINES AND  COSTS. 

The  following  cost  data  comprise  such  miscellaneous  items 
as  do  not  properly  come  in  the  preceding  chapters.  They  are 
given  not  as  including  all  the  miscellaneous  purposes  for 


Wire  Rope  ~ 


Comp.Air  f 
-Drill,  hung  [ 
on  Guides. 


!i         Side  Elevation, 
.% Rod  5vwy  Braces 


Front 
Elevation . 


Plan. 
Fig.    303.— Device    for   Drilling   Green    Concrete. 

which  concrete  is  used  but  as  being  such  items  of  costs  as 
were  secured  in  collecting  the  more  important  data  given  in 
preceding  sections. 

DRILLING  AND  BLASTING  CONCRETE.— Concrete  is 
exceedingly  troublesome  material  in  which  to  drill  deep  holes, 
and  this  statement  is  particularly  true  if  the  concrete  is  green. 

653 


654  CONCRETE    CONSTRUCTION. 

The  following  mode  of  procedure  proved  successful  in  drilling 
il/2-\n.  anchor  bolt  holes  6  ft.  and  over  in  depth  in  green  con- 
crete. The  apparatus  used  is  shown  by  Fig.  303,  re-drawn 
from  a  rough  sketch  made  on  the  work  by  one  of  the  authors, 
and  only  approximately  to  scale.  The  drill  is  hung  on  a 
small  pile  driver  frame,  occupying  exactly  the  position  the 
hammer  would  occupy  in  a  pile  driver,  and  is  raised  and  low- 
ered by  a  hand  windlass.  By  this  arrangement  a  longer  drill 
could  be  used  than  with  the  ordinary  tripod  mounting  and  less 
changing  of  drills  was  necessary.  A  wide  flare  bit  was  used, 
permitting  a  small  copper  pipe  to  be  carried  into  the  hole  with 
the  drill ;  through  this  pipe  water  was  forced  under  pressure, 
carrying  off  the  chips  so  rapidly  that  no  wedging  was  possible. 
By  this  device  drilling  which  had  previously  cost  over  25  cts. 
a  hole  was  done  at  a  cost  of  less  than  5  cts.  a  hole. 

In  removing  an  old  cable  railway  track  in  St.  Louis,  Mo., 
holes  8  ins.  deep  were  drilled  in  the  concrete  with  a  No.  2 
Little  Jap  drill,  using  a  i^-in.  bit  and  air  at  90  Ibs.  pressure. 
A  dry  hole  was  drilled,  the  exhaust  air  from  the  hollow  drill 
blowing  the  dust  from  the  hole  keeping  it  clean.  The  con- 
crete was  about  18  years  old  and  very  hard.  Two  holes  across 
track  were  drilled,  one  10  ins.  inside  each  rail ;  lengthwise  of 
the  track  the  holes  were  spaced  24  ins.  apart,  or  four  pairs  of 
holes  between  each  pair  of  yokes. 

Common  labor  was  used  to  run  the  drills  and  very  little  me- 
chanical trouble  was  experienced.  Three  cars  were  fitted  up, 
one  for  each  gang,  each  car  being  equipped  with  a  motor- 
driven  air  compressor,  water  for  cooling  the  compressors  being 
obtained  from  the  fire  plugs  along  the  route.  The  air  com- 
pressors were  taken  temporarily  from^  those  in  use  in  the  repair 
shops,  no  special  machines  being  bought  for  the  purpose. 
Electricity  for  operating  the  air  compressor  motors  was  taken 
from  the  trolley  wire  over  the  tracks.  The  car  was  moved 
along  as  the  holes  were  drilled,  air  being  conveyed  from  the 
car  to  the  drills  through  a  flexible  hose.  Two  drills  were 
operated  normally  from  each  car.  One  of  the  air  compressors 
was  exceptionally  large  and  at  times  operated  four  drills.  The 
total  number  of  holes  drilled  in  the  reconstruction  of  the  track 
was  31,000.  The  total  feet  of  hole  drilled  was  20,700  ft. 


MATERIALS,    MACHINES    AND    COST.  655 

With  the  best  one  of  the  plants  operating  two  to  three 
drills  30  8-in.  holes,  or  20.3  ft.  of  hole,  were  drilled  per  hour 
per  drill  at  a  labor  cost  of  2.7  cts.  per  foot. 

For  blasting,  a  o.i-lb.  charge  of  40  per  cent,  dynamite  was 
used  in  each  hole.  A  fulminating  cap  was  used  to  explode  the 
charge,  and  12  holes  were  shot  at  one  time  by  an  electric 
firing  machine.  The  dynamite  was  furnished  from  the  factory 
in  o.i-lb.  packages,  and  all  the  preparation  necessary  on  the 
work  was  to  insert  the  fulminating  cap  in  the  dynamite,  tamp 
the  charge  into  the  hole  and  connect  the  wires  to  the  firing 
machine.  In  order  to  prevent  any  damage  being  done  by 
flying  rocks  at  the  time  of  the  explosion,  each  blasting  gang 
was  supplied  with  a  cover  car,  which  was  merely  a  flat  car 
with  a  heavy  bottom  and  side  boards.  When  a  charge  was  to 
be  fired,  this  car  was  run  over  the  12  holes  and  the  side  boards 
let  down,  so  that  the  charge  was  entirely  covered.  This  work 
was  remarkably  free  from  accidents.  There  were  no  personal 
accident  claims  whatever,  and  the  total  amount  paid  out  for 
property  damages  for  the  whole  six  miles  of  construction  was 
$685.  Most  of  this  was  for  glass  broken  by  the  shock  of 
explosion.  There  was  no  glass  broken  by  flying  particles. 
The  men  doing  this  work,  few  of  whom  had  ever  done  blast- 
ing before,  soon  became  very  skillful  in  handling  the  dyna- 
mite, and  the  work  advanced  rapidly.  The  report  made  by 
the  firing  of  the  12  holes  was  no  greater  than  that  made  by 
giant  fire-crackers. 

For  the  drilling  and  blasting  the  old  rail  had  been  left  in 
place  to  carry  the  air  compressor  car  and  the  cover  car.  After 
the  blasting,  this  rail  was  removed  and  the  concrete  exca- 
vated to  the  required  depth.  In  most  cases  the  cable  yokes 
had  been  broken  by  the  force  of  the  blast.  Where  these  yokes 
had  not  been  broken,  they  were  knocked  out  by  blows  from 
pieces  of  rail.  The  efficacy  of  the  blasting  depended  largely 
upon  the  proper  location  of  the  hole.  Where  the  holes  had 
been  drilled  close  to  the  middle  of  the  concrete  block,  so  that 
the  dynamite  charge  was  exploded  a  little  below  the  center 
of  gravity  of  the  section,  the  concrete  was  well  shattered  and 
could  be  picked  out  in  large  pieces.  Where  the  hole  had  been 
located  too  close  to  either  side  of  the  concrete  block,  how- 


656 


CONCRETE    CONSTRUCTION. 


ever,  the  charge  would  blow  out  at  one  side  and  a  large  mass 
of  solid  concrete  would  be  left  intact  on  the  other  side.  The 
total  estimated  quantity  of  concrete  blasted  was  6,558  cu.  yds., 
or  0.2  cu.  yd.  of  concrete  per  lineal  foot  of  track.  The  cost 
of  the  dynamite  delivered  in  o.i  Ib.  packages  was  13  cts.  per 
pound.  The  exploders  cost  $0.0255  each. 

The  cost  of  drilling  and  blasting  was  as  follows : 

Item.  Per  mile.      Per  lin.  ft.     Per  cu.  yd. 

Labor,  drilling  $  89.76  $0.017  $0.085 

Blasting  labor  and  materials.  285.12  0.054  0.268 


Total  drilling  and  blasting. $374.88  $0.071 


$0-353 


^liiM 

:&M&jA 


Fig.  304.— Bench  Monument,  Chicago,   111. 

The  cost  of  blasting  with  labor  and  materials,  separately 
itemized,  was  as  follows,  per  cubic  yard : 

Dynamite  and  exploders . .  .$0.192 

Labor    0.076 

Total , . .  .$0.268 

Two  cubic  yards  of  concrete  were  blasted  per  pound  of 
dynamite. 

BENCH  MONUMENTS,  CHICAGO,  ILL.— The  standard 
bench  monuments,  Fig.  304,  used  in  Chicago,  111.,  are  mostly 
placed  in  the  grass  plot  between  the  curb  and  the  lot  line,  so 
that  the  top  of  the  iron  cover  comes  just  level  with  the 
street  grade  or,  flush  with  the  surface  of  the  cement  walk. 
The  monument  consists  of  a  pyramidal  base  6  ft.  high 


MATERIALS,    MACHINES    AND    COST. 


657 


and  42  ins.  square  at  the  bottom,  with  a  %  -in.  x  2-ft.  cop- 
per rod  embedded,  and  of  a  cast  iron  top  and  cover  con- 
structed as  shown  by  the  drawing.  Mr.  W.  H.  Hedges,  Bench 
and  Street  Grade  Engineer,  Department  of  Public  Works, 
Chicago,  111.,  gives  the  following  data  regarding  quantities  and 
cost.  The  materials  required  for  each  monument  are:  1.78  cu. 
yd.  crushed  stone,  0.6  cu.  yd.  torpedo  sand,  il/2  bbls.  cement, 
60  ft.  B.  M.  lumber,  one  J4  x  24-in.  copper  rod,  one  top  and 
cover.  A  gang  consisting  of  i  foreman,  4  laborers  and  2  teams 


HH 

:.-*•' .•••.!•  •••-.•'.••. 


mm 
wm 


Vertical 
Section 


t-IO '  -J 
Pig.   305.— Base  for  Wooden  Pole. 


Elevation 

Fig.    306.— Mile    Post,    Chicago    & 
Eastern    Illinois    Ry. 


construct  from  one  to  three  monuments  per  day,  the  average 
number  being  two  per  8-hour  day.  In  1906  the  average  cost 
of  the  monuments  was  $24.12  each,  based  on  above  material 
and  labor  charges. 

POLE  BASE.— Figure  305  shows  a  concrete  base  for  trans- 
mission line  poles  invented  by  Mr.  M.  H.  Murray,  of  Bakers- 
field,  Cal.,  and  used  by  the  Power  Transit  &  Light  Co.  of  that 
city.  These  bases  are  molded  and  shipped  to  the  work  ready 


658  CONCRETE    CONSTRUCTION. 

for  placing.  They  weigh  about  420  Ibs.  each.  One  base  re- 
quires 37^  Ibs.  of  2x]4-m-  steel  bar,  40  Ibs.  of  Portland 
cement,  3  cu.  ft.  of  broken  stone  or  gravel  and  enough  sand  to 
fill  the  form  or  mold,  which  is  lox  10  ins.  by  4^2  ft.  Unskilled 
labor  is  employed  in  the  molding  and  two  men  can  mold  ten 
bases  per  8-hour  day.  The  cost  of  molding  is  as  follows  per 
base: 

2  men  at  $2  per  day $0.40 

Brace  irons  per  set 2.50 

1-9  cu.  yd.  stone  at  $4.05 0.45 

40  Ibs.  cement  at  \y2  cts 0.60 

Sand    0.15 

Total  cost   $4.10 

,Two  men  at  $2  per  day  each  set  five  bases  in  eight  hours, 
making  the  cost  of  setting  80  cts.  per  base.  The  bases  were 
sunk  to  a  depth  of  3  ft.  3  ins.  In  many  cases  they  were 
placed  under  poles  without  interrupting  service  by  sawing  off 
the  pole,  dropping  it  into  the  ground,  placing  the  new  base 
and  setting  the  sawed-off  pole  on  it  and  bolting  up  the  straps. 

MILE  POST,  CHICAGO  &  EASTERN  ILLINOIS  R.  R. 

— The  dimensions  of  the  post  are  shown  by  Fig.  306.  Each 
post  weighs  498  Ibs.  They  are  made  when  other  concrete 
work  is  being  done.  The  form  is  laid  flat,  with  the  molds  for 
the  letters  on  the  bottom,  and  bottom  and  sides  are  plastered 
with  mortar,  which  is  backed  up  with  a  1-1-2  stone  concrete. 
The  cost  of  the  post  is  given  as  follows : 

l/4  barrel  of  cement  at  $2 $0.50 

267  Ibs.  crushed  stone ». o.oi 

1 33  Ibs.   sand    o.oi 

i  1-3  hours  labor  at  15  cts 0.20 

1-3  hour  carpenter  changing  letters  at  25  cts 0.08 

Coloring  cement    ,  0.02 


Total    $0.82 


MATERIALS,    MACHINES    AND    COST.  659 

BONDING     NEW     CONCRETE    TO     OLD.— Concrete 

which  has  set  hard  has  a  surface  skin  or  glaze  to  which  fresh 
concrete  will  not  adhere  strongly  unless  special  effort  is  made 
to  perfect  the  bond.  Various  ways  of  doing  this  are  prac- 
ticed. The  most  common  is  to  clean  the  hardened  surface 
from  all  loose  material  and  give  it  a  thorough  wash  of  cement 
grout  against  which  the  fresh  concrete  is  deposited  and 
rammed  before  the  grout  has  had  time  to  set.  Washing  the 
old  surface  with  a  hose  or  scrubbing  it  with  a  brush  and 
water  improves  the  bond,  as  does  also  the  hard  tamping  of  the 
concrete  immediately  over  the  joint.  Mortar  may  be  used  in 
place  of  grout.  The  thorough  cleansing  of  the  surface  is,  how- 
ever, quite  as  essential  as  the  bonding  coat,  in  fact  in  the 
opinion  of  the  authors  it  is  more  essential.  As  a  rule,  a  good 
enough  joint  for  ordinary  purposes  can  be  got  by  tamping  the 
fresh  concrete  directly  against  the  old  concrete,  without  grout 
or  mortar  coating,  if  the  surface  of  the  latter  is  thoroughly 
y-cleaned  by  scrubbing  and  flushing.  The  secret  of  securing  a 
good  bond  between  fresh  concrete  and  concrete  that  has  set 
lies  largely  in  getting  rid  of  the  glaze  skin  and  the  slime  and 
dust  which  forms  on  it.  Washing  will  go  far  toward  doing 
this.  The  glaze  skin  can  be  removed  entirely  by  acid  solu- 
tions, but  the  acid  wash  must  be  flushed  free  from  the  surface 
before  placing  the  fresh  concrete.  Ransomite,  made  by  the 
Ransome  Concrete  Machinery  Co.,  Dunellen,  N.  J.,  is  a  pre- 
pared acid  wash  which  to  the  authors'  knowledge  has  given 
excellent  success  in  a  number  of  cases.  The  glaze  coat  can 
also  be  removed  by  picking  the  hardened  surface,  but  the  pick- 
ing should  be  followed  by  washing  to  remove  all  loose  chips 
and  dust. 

DIMENSIONS   AND    CAPACITIES   OF   MIXERS.— In 

planning  plant  lay-outs  it  is  often  desirable  to  knew  the  sizes, 
capacities,  etc.,  of  various  mixers  in  order  to  make  preliminary 
estimates.  Tables  XXII  to  XXXIII  give  these  data  for  a 
number  of  the  more  commonly  employed  machines.  The 
Eureka,  the  Advanced  and  the  Scheiffler  mixers  are  continu- 
ous mixers  and  the  others  are  batch  mixers. 


66o 


CONCRETE    CONSTRUCTION. 


TABLE  XXII — SIZES,  CAPACITIES  AND  WEIGHTS  OP  ADVANCED  MIXERS. 
Cement  Machinery  Co.,  Jackson,  Mich. 

Height  ground  to  hopper  top 3'  6" 

Width   over  all 3'  6" 

Length  over  all  on  trucks ! . 10'  6" 

Capacity  per  hour,   cu.  yds 25  to  75 

Horsepower,    engine    

Weight : 

On  trucks,  without    power,    Ibs ]  ,700 

On  trucks,  steam  engine    2^000 

On  trucks,  gas    engine 2,200 

On  trucks,  steam   engine  and   boiler 2,500 

TABLE  XXIII — SIZES,  CAPACITIES  AND  WEIGHTS  OP  SCHEIFFLER  PROPORTIONING  MIXERS. 
The  Hartwick  Machinery  Co.,  Jackson,  Mich. 

Mixer  Number.  No.  2.            No.  2l/2.  No.  3. 

Dimensions  of  hopper,   ins 55  x  33              53  x  33  60  x  40 

Height,  from  ground  to  top  of  hopper,  ins.  43                      43  48 

Width  over  all  on  trucks,   ins 46                      46  46 

Length  over  all  on  trucks,  ins 126                    126  132 

Hourly  capacity  in  cubic  yards 5-6                        8  12-15 

Horsepower  required,  gasoline  engine....  234 

Horsepower  required,  steam  engine ..                       3  4 

Weights: 

On  trucks,   without  power,  Ibs 2,400                 2,900  3,300 

On   trucks,   gasoline  engine,   Ibs 3,000                 3,600  4,500 

On  trucks,   steam   engine,    Ibs 2,800                 3,330  4,000 

On  trucks,  steam  engine  and  boiler,  Ibs..  3,500                 3,700  4,800 


TABLE  XXIV — SIZES,  CAPACITIES  AND  WEIGHTS  OF  EUREKA  MIXERS. 
Eureka  Machine  Co.,  Lansing,  Mich. 


Mixer  Number    .  .  .  .  ' 

No.  81 

No.  82 

No.  83 

No   84 

No   25 

No   23 

fSand  
Size  hoppers,  ins.  {  Cement.  .»  
[Stone  
Height,  ground  to  hopper  top  . 
Width  over  all  on  trucks  
Length  over  all  on  trucks  
Capacity  per  hour,  cu.  yds  .... 

18"x25i" 
17"x25i" 
30"x25" 
49" 
40" 
12'—  9" 
10  to  18 
3  stm. 

do 

49" 
40" 
10'—  0" 
10  to  18 

3  stm. 

do 

49" 
40" 
10'—  0" 
10  to  18 
3J  gas 

do 

49" 
40" 
10'—  0" 
10  to  18 
3  el.motr 

18"x25*" 
17"x25*" 

"49"" 
40" 
8'—  0" 
10  to  18 
Pulley 

18"x25r 
17"x25$" 

"49"" 
4(T 
8'—  0* 

2  to  4 
Hand 

4 

Weight  on  trucks,  no  power.  .  .  . 
Weight  trucks  steam  engine.  .  .  . 
Weight  trucks  gas  engine  
Weight  trucks  eng  and  boiler.  . 

1,980 
2.800 

3,000 

1,980 

1,980 
2,  300 

1,980 

1,400 

1,400 

TABLE  XXV — SIZES,  CAPACITIES  AND  WEIGHTS  OF  SNELL  MIXERS. 
R.  Z.  Snell  Mfg.  Co.,  South  Bend,  Ind. 


yds. 


Mixer    Number. 

Size  batch,   cu.   ft 

Capacity  per  hour,  cu. 

Speed   revs,   per   min 

Weight  on  Skids: 

With    pulley,    Ibs 

With  engine,  Ibs 

With  eng.   and  boiler,   Ibs 

Weight  en  Wheels: 

With   engine,   Ibs 

With  engine  and  boiler,  Ibs 

Engine: 

Size  cylinder,  ins 

Rated    horsepower    

Boiler: 

Size,    ins 

Rated  horsepower  

Outside    dimensions    on   skids.... 
Total  height  on  skids 


No.  0. 
3 

2% 
30 

480 

800 


1,100 


4x6* 
1% 


2'9"  x  4' 
3'8" 


No.  1. 

7 

5 

30 

800 
1,550 
2,170 

2,200 
3,570 

3%  x  4i 


24x60 
5 

3'4"  x  5'6" 
4'6" 


No.  2. 

11 

8 

25 

900 

2,050 
2,900 

3,450 
4,750 

4x5 
5 

26x60 

e 

4'x6' 
5' 


No.  3. 
24 
20 
19 

2,000 
3,500 
4,000 

4,700 
5,200 

5x6^ 
6 

30x60 

8 

6'x9' 
5'6" 


MATERIALS,    MACHINES    AND    COST. 


661 


TABLE  XXVI—  SIZES,  CAPACITIES  AND  HORSEPOWER  OP  RANSOME  MIXERS. 
Ransome  Concrete  Machinery  Co.,  Dunellen,  N.  J. 


Mixer  number. 
Size  batch,  cu.  ft 
Capacity  per  hr.,  cu.  yds 
Speed,   Revs,   per   min 

Weight  on  Skids: 
Pulley  or  gear,  Ibs 
With  engine,  Ibs 
With  engine  and  boiler,   Ibs 

Weight   on  Wheels: 
With   engine,    Ibs 
With  engine  and  boiler,  Ibs 

Engines: 

Size   cylinder,   ins 
Rated   horsepower 

Boiler: 
Size,    ins  ................  . 

Rated   horsepower 


10 


to  14 
10 
16 

3,300 
4,600 
6,450 

5,100 
6,950 

6x6 

7 

36  x  69 

10 


No.  2. 
20 
20 
15 

No.  3. 
30 
30 

No.  4. 
40 
40 
14 

3,650 

5,050 
8,700 

5,900 
7.700 
12,200 

7.400 
9,250 
14,700 

5,550 
9,200 

8,200 
12,700 

9,750 

15,000 

7x7 
10 

8x8 

14 

9x9 
20 

42x75       42x87       48x93 
15  20  30 


TABLE  XXVII — SIZES,  CAPACITIES  AND  HORSEPOWERS  OF  CHICAGO  IMPROVED  CUBE  MIXERS. 
Municipal  Engineering  and  Contractng  Co.,  Chicago,  111. 


Mixer    number.            "] 
Size    batch,    cu.    ft  *. 

Handy.' 

2% 

'  No.  6.  1 
3 

fo.  11.  ] 
11 

So.  17.  : 

17 

No.  22.  ] 

22 

sro.  33.  : 

33 

No.  64. 
64 

Capacity  per  hr.,  cu.  yds. 
Speed,  revs,  per  min  .... 

5% 
24 

13 

20 

24 
18 

40 
17 

50 
16 

70 
15 

120 
12 

Weight  on  Skids: 
Pulley   or   gear     Ibs 

1  000 

1  900 

2  800 

5  000 

7  000 

9  600 

19  000 

With    engine     Ibs  ' 

2  500 

3  600 

6  100 

8  200 

12  000 

With  eng.  and  boiler,  Ibs. 

3,100 

4,300 

7,800 

10,000 

16,000 

Weight  on  Wheels: 
With  engine,   Ibs  

1  400 

3  200 

4  500 

7  100 

9  500 

15  000 

With  eng.  and  boiler,  Ibs. 
Engine: 
Size  cylinder,  ins  

4,000 
4x4 

6,000 
6x6 

8,800 
6i&  x  7 

10,300 

7x8 

17,000 
8x9 



Rated    horsepower    

2 

3 

6 

8 

12 

15 

30 

Boiler,    rated   horsepower 
Width  over  all    

4'-5' 

4 

8 

10 

15 
8'-6" 

18 
9"-  8" 

35 

Length   over    all 

"     6'-S" 

8'-0" 

'     8'-  10' 

Height  bot.  sill  to  charg- 
ing hopper  

3'  4' 

4"  3'-5" 

> 

)"  4'-7" 

5'-0' 

5'  -9" 

Additional     height     on 
wheels    . 

9 

7s"  l'-5Vi 

'"  r-si 

TABLE  XXVIII — SIZES,  CAPACITIES  A  JD  HORSEPOWERS  OF  CROPP  MIXERS. 
A.  J.  Cropp,  Concrete  Machinery,  Chicago,  111. 


Mixer   number.  No.  0. 

Size  batch,  cu.   ft 7  to  8 


yds.. 


15 

12 


1,375 

2,575 


Cap.    per   hr.,    cu. 

Speed,  revs,   per  min 

Weight  on  Skids: 

With    engine,    Ibs 

With  eng.  and  boiler,  Ibs 

Weight  on  Wheels: 

With    engine,    Ibs 1,775 

With  eng.  and  boiler,  Ibs 2,900 

Engine: 

Size  cylinder,   ins 4x4 

Rated  horsepower 3 

Boiler: 

Size    inside    24"  x  4' 

Rated    horsepower    

Out.    dimensions    on   skids 40" 

Total    height     50" 

Height  fr.   ground  on  trucks: 

Charging,    ins 20 

Discharging,  ins 30 


No.  1. 
10 
20 
10 

1,650 
2,950 

2,050 
3,350 

5x5 
5 


24 


x  6' 

6 
40" 

56" 

20 
30 


No.  2. 

No.  3, 

,     No.  4. 

13 

16 

20 

25 

30 

40 

10 

10 

10 

1,700 

1,975 

2,100 

3,000 

3,775 

3,900 

2,200 

2,475 

2,600 

3,400 

4,250 

4,350 

5x5 

6x6 

6x6 

5 

7 

7 

24"  x  6' 

30"  x  6" 

30"  x  6" 

6 

9 

9 

40" 

48" 

48" 

56" 

56" 

62" 

20 

20 

20 

30 

30 

30 

662  .  CONCRETE    CONSTRUCTION. 

TABLE  XXIX — SIZES,  CAPACITIES  AND  HORSEPOWERS  OP  CHICAGO  CONCRETE  MIXERS. 
Chicago  Concrete  Machinery  Co.,  Chicago,  111. 

Number  of  mixer.                                     No.  00.  No.  0.  No.  1. 

(  cement     y2  1  1 

Standard  charge  in  cu.  ft.    •<  Sand   1%  2%  4 

(  stone    3  5  8                 16 

Total  unmixed,  batch  in  cu.   ft 5  8%  13                 26 

Mixed  concrete  per  batch,  loose  in  cu.  ft.        SV2  G  9                 18 
Cubic   yards   of  unmixed   material   per 

hour,  45  batches  per  hour   8  14  21                  42 

Cubic  yards  of  mixed  concrete  per  hour, 

45  batches  per  hour  6  10  15                 30 

Minimum   horsepower   required 2  4  6                   8 

Revolutions  of  driving  pulley    permin...    209  190  185               170 

Revolutions  of  drum  per  min 20  18  15                 13 

Diameter  and    face    of   driving  pulley. .  .20  x  3%     20x4%'    24x5^       28x6% 
>     Weight: 

On  skids  with  pulley,  Ibs 1,550  2,150  2.900            4,850 

On  truck  with  pulley  or  gears,  Ibs 1,300  2550  3,500             5,150 

On  skids  with  st.   engine   only,    Ibs 2,400  3,400             4,600 

On  truck  with  st.   engine  only 2,900  4,000            5.300 

On   skids  with  st.   eng.   and   boiler,   Ibs 2,800  4,700             6,000 

On  truck  with  st.    eng.    and  boiler.   Ibs.. 2. 400  4,200  5.750             7,850 

On   skids    with    gasoline    engine.    Ibs 2,000  3.500  5,000             6,500 

On  truck  with  gasoline  engine,  Ibs 2,400  4.300  5,800            7,800 

TABLE  XXX — SIZES,  CAPACITIES  AND  HORSEPOWERS  OF  KOEHRING  MIXERS. 

Koehring  Machine  Co.,  Milwaukee,  Wis. 

Mixer   number.                                                  No.  0-B.  No.  1-B.  No.  2-B.  No.  3-B. 

Capacity  per  charge,   in  cu.    ft 7  11  22                 27 

Capacity  per  hour  in  cu.  yds 7  14  25                 30 

Horsepower,    steam   engine 4  6  8                 10 

Horsepower,    steam    boiler    5  8  10                 14 

Horsepower,    gasoline    engine 4  6  10                 12 

Horsepower,    electric    motor    5  6  7%              10 

Speed   of  drum    20  17  15                  15 

Speed  of  intermediate  shaft   . .  / 132  108  75                 75 

Weight   of   mixer   on   skids 1,800  2.800  5.200             5,500 

Weight  of  mixer  on  skids,  with  steam  eng.2,300  3,550  6,500             7,000 
Weight  of  mixer  on  skids,  with  steam  en- 
gine   and    boiler     3,300  5,000  8,000            9,300 

Weight  of  mixer  on  skids,  gasoline  engine 

and  housing    3,000  4,400  7,500             8,600 

Weight  of  trucks  with  pole   400  600  850                950 

Weight     of    automatic     loading    bucket 

complete     500  700  1,000             1,100 

Weight  of  mixing  through  complete 200  250  400                400 

TABLE  XXXI — SIZES,  CAPACITIES  AND  HORSEPOWERS  OP  SMITH  MIXERS. 
Contractors'  Supply  &  Equipment  Co.,  Chicago,  111. 

Mixer   number.  No.  0.       No.  1.       No.  2.       No.  2%.     No.  4.     No.  5. 

Qtnnrl     r-hnrr^       I     Cement..  112234 

cu  f t             1   Sand     •••2%              4                  6  7%  10%            14 

I   Stone    ...         5                  8                12  15  21                28 

Total    unmixed    per    batch, 

cu.     ft 8V2            13                20  .  24y2  .        34i/2            46 

Mixed    material    per    batch 

(loosi),  cu.  ft 6                  9                131/2  16%  22                30 

Cubic      yards      mixed      per 

hour,  up  to 9                20                30  39  46                62 

Power    required— H. P.     ...         4                  6                  8  10  15                19 

Revs,  per  minute  of  driving 

pulley     218              180              173  162  160              125 

Diameter  and  face  of  driv- 
ing pulley,  ins 20  x  4%     24  x  5%     28  x  5%  28  x  6%  36  x  6%  48  x  7% 

Weight  on  skids  with  pul- 
ley only.   Ibs 1,740           2,500           3,600  4,400  6,200           7,900 

Weight  on 'truck  with  pul- 
ley or   gears,    lus 2,200           3,650           4,750  5,500  7,400 

Weight      on      truck      with 

steam  eng.  &  boil.,  ltrs.3,750           5,600           7,200  8,600  11,400 

Weight  on  truck  with  gaso- 
line engine,   Ibs 4,000          5,100          7.400  9.300            ....            


UNIVERSITY  A 

J 

>e  ?i^>/ 

MATERIALS,    MACHINES    AND    COST.  663 


TABLE  XXXII— SIZES,  WEIGHTS  AND  CAPACITIES  OP  POLYGON  MIXER. 
Waterloo  Cement  Machinery  Co.,  Waterloo,  Iowa. 

Mixer   number.                                              No.  4.  No.  5.       No.  6.          No.  7. 

Maximum   charge,    cu.    ft 6  10                 12                 16 

Cubic  yards  mixed  per  day  (10  hrs.)  up  to      60  190               130               180 

Weight     on   skids   with  pulley    (approx.)..  1,600  2,200             3,500             4000 
Weight     on  skids  with  steam  engine   and 

boiler    (approx.)     3,100  3,900             5,500             6.200 

Weight    on    skids     with     gasoline     engine 

(approx.)      2,900  3,900             5,100             5,700 

Weight  on  trucks  with  steam  engine  and 

boiler    (approx.)     3,600  4,600             6,000             7,000 

Weight   on    trucks    with     gasoline     engine 

(approx.) 3,400  4,650             5,700             6,750 

DATA  FOR  ESTIMATING  THE  WEIGHT  OF  STEEL 
IN  REINFORCED  CONCRETE.— Architects'  and  engineers' 
plans  record  the  steel  used  in  reinforced  concrete  in  various 
ways.  Sometimes  complete  schedules  of  shapes,  dimensions 
and  weights  of  the  various  reinforcing  elements  are  drawn  up 
and  submitted  to  bidders  with  the  plans.  In  such  cases  the 
estimating  is  usually  a  simple  problem  for  the  contractor.  In 
other  cases  the  amount  of  steel  that  will  be  required  is  stated 
as  a  percentage  of  the  volume  of  the  concrete.  In  still  other 
cases  the  detail  drawings  merely  show  the  number,  location 
and  dimensions  of  the  reinforcing  bars,  stirrups,  etc.,  and  the 
contractor  has  to  compile  from  them  his  own  schedule  of 
quantities.  The  following  tables  and  discussion  will  aid  the 
contractor  in  making  his  estimates.  Before  proceeding  with 
these  data,  however,  the  authors  would  strongly  advise  that  to 
facilitate  rapid  estimating  the  contractor  should  keep  accurate 
records  of  all  reinforced  concrete  structures  in  such  form  as 
to  show  the  percentages  of  steel  used.  In  doing  this,  however, 
he  should  be  careful  to  separate  the  foundations,  etc.,  which 
are  not  reinforced  from  the  superstructure  which  is  reinforced. 
A  reinforced  concrete  arch  bridge,  for  example,  usually  rests 
on  piers  and  abutments  which  are  not  reinforced.  Do  not 
lump  together  all  the  concrete  in  recording  the  weight  of  rein- 
forcement used,  but  separate  the  reinforced  arch  from  the  un- 
reinforced  portions. 

Method  of  Computing  Weight  from  Percentage  of  Volume. 
— In  a  cubic  yard  of  concrete  there  is  I  per  cent,  of  27  cu.  ft. 
or  0.27  cu.  ft.  of  steel  if  the  reinforcement  is  I  per  cent.  Now 
a  cubic  foot  of  steel  weighs  490  Ibs.,  but  for  all  practical  pur- 
poses we  can  call  it  500  Ibs.  Hence  reinforced  concrete  con- 
taining i  per  cent,  of  steel  has  0.27  X  500=  135  Ibs.  per  cubic 
yard.  Table  XXXIII  has  been  computed  in  this  manner; 
knowing  the  price  of  steel  it  is  a  matter  of  simple  multiplica- 


664  CONCRETE    CONSTRUCTION. 

tion  to  estimate  from  the  table  the  cost  of  steel  for  any  per- 
centage of  reinforcement. 

Weights  and  Dimensions  of  Plain  and  Special  Reinforcing 
Metals.  —  Steel  for  reinforcement  is  used  in  the  shape  of  plain 
round  and  square  bars,  deformed  bars,  woven  and  welded  net- 
ting and  metal  mesh  of  various  sorts.  Tables  XXXIV  to 
XXXVII  show  the  weights,  dimensions,  etc.,  of  these  various 
metals. 

TABLE  XXXIII  —  SHOWING  WEIGHT  OF  STEEL  PER  CUBIC  FOOT  AND  PER  CUBIC  YARD  OF 

CONCRETE  FOR  VARIOUS  PERCENTAGES  OF  REINFORCEMENT. 

Per  cent  Lbs.  steel  Lbs.  steel 

of  steel.  Per  cu.  ft.  Per  cu.  yd. 

.0.20  1.00  27.0 

0.25  1.25  33.8 

0.30  1.50  40.5 

0.35  1.75  47.3 

0.40  2.00  54.0 

0.45  2.25  60.8 

0.50  2.50  67.5 

0.55  2.75  74.3 

0.60  3.00  81.0 

0.65  3.25  87.5 

0.70  3.50  94.5 

0.75  3.75  101.3 

0.80  4.00  108.0 

0.85  4.25  114.8 

0.90  4.50  121.5 

0.95  4.75  128.3 

1.00  5.00  135.0 

TABLE  XXXIV—  WEIGHTS  OF  ROUND  AND   SQUARE  BARS   OF   DIMENSIONS   COMMONLY 

USED  FOR  REINFORCING  CONCRETE. 

Thickness  or  Weight  of  square  Weight  of  round 

diameter  in  inches  bars.  Lbs.  per  ft.  rods.  Lbs.  per  ft. 

1-16  0.013  0.010 

V8  0.053  0.042 

3-16  0.119  0.094 

%  0.212  0.167 

5-16  0.333  0.261 

%  0.478  0.376 

7-13  0.651  0.511 

y2  0.850  0.668 

9-16  -                                  1.076  0.845 

%  1.328  1.043 

11-16  1.607  1.262 

%  1.913  1.502 

%  2.608  2.044 

1  3.400  2.670 
1U  4.303  3.380 
iS  5.312  4.172 
1^  7.650  6.008 
ll  10.404  4.178 

2  13.600  10.68 

TABLE  XXXV—  DIMENSIONS  AND  WEIGHT  OF  EXPANDED  METAL. 

Mesh,  Sectional  area  sq.  Weight,  Ibs. 

inches.  ins.  per  ft.  width.         per  sq.  ft. 

Vz  0.209  0.74 


•  n  00_  «  Sft 

::::::  :::::::::::::::::::  il  :  : 

Standard   ..........................  2  -«  0,56 


2:f 


ExfrY  heavy'  '  '.  '.  '.  '.  '.  '.  '.  '.  '.  '.  '.  '.  '•  '•  '.  '.  .'.  '.  '•  •  0.356  1.20 


MATERIALS,    MACHINES    AND    COST. 


665 


TABLE  XXXVI — DIMENSIONS  AND  WEIGHT  OP  KAHN  RIB  METAL. 

Section  area  Weight  per 


Size 

No. 

2 

3 

4 

5 

6 

7 


per  ft.  width  sq.  ins. 

0.54 
.  0.36 
0.27 
0.22 
0.18 
0.15 
0.14 


sq.  ft.  Ibs. 
2.13 
1.43 
1.08 
0.87 
0.72 
0.62 
0.55 


TABLE  XXXVII- 


-WEIGHTS  OF   DEFORMED   BARS  OF   DIMENSIONS   COMMONLY  USED  FOR 
REINFORCED  CONCRETE. 


Size, 
ins. 


Weight,  Ibs. 
per  ft. 


Area 
sq.  ins. 


Size 
ins. 


Weight,  Ibs. 
per  ft. 


Area 
sq.  ins. 


Ransome  Twisted  Bar. 


New  Style  Corrugated  Bar. 


0.212 

0.85 

1.32 

1.91 

2.6 

3.4 

5.3 


0.063 

0.25 

0.319 

0.563 

0.765 

1.000 

1.563 


0.24 
0.85 
1.33 
1.91 
2.60 
3.40 
5.31 


0.06 
0.25 
0.39 
0.56 
0.77 
1.00 
1.56 


Diamond  Bar. 


Universal  Corrugated  Bar. 


0.85 
1.33 
1.91 
2.60 
3.40 
5.31 


0.25 
0.39 
0.56 
0.76 
1.00 
1.56 


5-16x114 


x2 


0.73 
1.18 
1.35 
1.97 
2.27 
2.85 


0.19 
0.32 
0.41 
0.54 
0.65 
0.80 


-No     1    Mill- 


Thacher  Bulb  Bar. 


-No.    2    Mill.- 


1 

7/8 

k 

!* 


0.16 
0.61 
0.95 
1.39 
1.87 
2.42 
3.74 
5.30 
7.07 
9.02 


0.047 

0.18 

0.28 

0.41 

0.55 

0.71 

1.10 

1.56 

2.08 

2.65 


0.58 
0.92 
1.34 
1.79 
2.32 
3.55 
5.20 


0.17 
0.27 
0.39 
0.53 
0.68 
1.04 
1.53 


666  CONCRETE    CONSTRUCTION. 

Monolith  Bar.  Twisted  Lug  Bar. 


0.4 


0.8 

1 


0.55 
0.85 


2.18 
3.37 


7.75 


0.25 
0.32 


0.64 
1.00 


2.25 


1 

1% 
1% 


Cup  Bar. 


0.222 

0.87 

1.35 

1.94 

2.64 

3.45 

5.37 

7.70 


0.625 

0.250 

0.3906 

0.5625 

0.7656 

1.00 

1.5625 

2.25 


0.48 
0.86 
1.35 
1.95 
2.65 
3.46 
4.38 
4.51 


RECIPES  FOR  COLORING  MORTARS.—  The  following 
recipes  for  coloring  cement  mortar  have  been  found  reliable  ; 
the  weights  given  being  weight  of  coloring  matter  per  bag  of 
cement  and  for  a  1-2  mortar: 

Brown  Stone:  4  to  5  Ibs.  brown  ochre  or  l/2  Ib.  best  quality 
roasted  iron  oxide. 

Buff  Stone:  4  Ibs.  yellow  ochre. 

Red  Stone:    5  Ibs.  raw  violet  iron  oxide. 

Bright  Red  Stone:   $y2  to  7  Ibs.  English  or  Pompeiian  red. 

Blue  Stone:  2  Ibs.  ultramarine  blue. 

Dark  Blue  Stone:  4  Ibs.  ultramarine  blue. 


Slate:  Lamp  black  T/2  Ib.  light  slate  ;  4  Ibs.  dark  blue  slate. 
Light  Terra  Cotta:  2,  Ibs.  Chattanooga  iron  ore. 


CHAPTER   XXV. 

METHODS  AND  COST  OF  WATERPROOFING  CON- 
CRETE STRUCTURES. 

Resistance  to  penetration  by  water  is  desirable  in  all  con- 
crete structures,  and  is  essential  in  such  structures  as  tanks, 
reservoirs,  vaults,  subways,  basements  and  roofs.  Concrete,  as 
it  is  ordinarily  made,  is  pervious  to  water,  hence  to  secure 
concrete  structures  through  which  water  will  not  penetrate 
some  method  of  waterproofing  the  concrete  must  be  em- 
ployed. Many  methods  have  been  proposed  and  are  being 
used ;  none  of  these  methods  is  without  faults,  the  best  one  of 
them  has  not  yet  been  determined,  and  the  evidence  available 
as  to  their  comparative  merits  is  biased  and  conflicting.  For 
these  reasons  any  discussion  of  waterproofing  for  concrete  is 
at  the  present  time  bound  to  be  unsatisfactory. 

Methods  of  waterproofing  may  be  roughly  classified  as  fol- 
lows:  (i)  Use  of  mixtures  so  proportioned  as  to  be  im- 
pervious; (2)  admixture  of  substances  designed  to  produce 
impermeability;  (3)  use  of  waterproof  coatings,  washes  or 
diaphragms.  In  succeeding  sections  enough  examples  of  each 
method  are  given  to  indicate  current  practice;  no  attempt  has 
been  made  to  catalog  all  the  waterproofing  substances  and 
systems  being  promoted — there  are  too  many  of  them. 

The  art  of  waterproofing  concrete  is  in  a  transition  stage. 
Outside  of  the  manufacturers  of  waterproofing  material  the 
art  has  received  serious  study  by  comparatively  few  persons. 
No  comparative  tests  by  independent  investigators  are  avail- 
able. Practical  experience  with  most  of  the  materials  used  has 
not  extended  over  a  long  enough  period  of  time  to  permit 
true  conclusions  to  be  drawn.  Students  of  the  subject  are  not 
even  agreed  upon  the  broad  questions  whether  it  is  better 
to  work  toward  developing  an  impervious  concrete  or  toward 
perfecting  a  waterproof  covering  for  concrete.  On  the  minor 
subdivisions  there  is  no  agreement  at  all. 

667 


668  CONCRETE    CONSTRUCTION. 

In  the  present  state  of  the  art  one  can  lay  fast  hold  to  only 
three  things.  The  first  is  that  waterproofing  is  one  component 
of  a  system  of  drainage ;  the  second  is  that  structures  must, 
to  get  the  best  results,  be  designed  with  the  fact  in  mind  that 
waterproofing  is  a  component  structural  element,  and  the 
third  is  that  skilled  and  conscientious  workmanship  are  essen- 
tial elements  in  the  success  of  all  waterproofing  materials  and 
methods. 

IMPERVIOUS  CONCRETE  MIXTURES.— The  com- 
pounding of  the  regular  concrete  materials  so  as  to  produce  an 
impervious  concrete  has  been  made  the  subject  of  numerous 
experiments.  The  most  elaborate  of  these  experiments  were 
those  conducted  over  a  period  of  five  years  by  Mr.  Feret,  of 
the  Boulogne  (France)  Laboratory  of  the  Fonts  et  Chaussees. 
Feret's  experiments  led  him  to  the  following  conclusions : 

"That  in  all  mortars  of  granulometric  composition  the  most 
permeable  are  those  which  contain  the  least  quantity  of 
cement. 

"Of  all  mortars  of  the  same  richness,  but  of  varying 
granulometric  composition,  those  which  contain  very  few  fine 
grains  are  much  more  permeable.  They  are  the  more  so 
where,  with  equal  proportions  of  the  fine  grains,  the  coarse 
grains  predominate  more  in  relation  to  the  grains  of  medium 
size. 

"The  minimum  permeability  is  found  in  mortars  where  the 
proportion  of  medium-sized  grains  is  small,  and  the  coarse  and 
fine  grains  are  about  equal  to  each  other." 

Mr.  Feret  also  found  that  permeability  decreased  with  time 
and  that  wet  mixtures  were  less  permeable  than  dry  mixtures. 

Tests  made  by  Messrs.  J.  B.  Mclntyre  and  A.  L.  True  at  the 
Thayer  School  of  Civil  Engineering  in  1902  gave  the  follow- 
ing results : 

All  the  specimens  composed  of  i-i  mortar  in  the  proportions 
°f  3°»  35»  4°  an(l  45  Per  cent,  of  the  whole  mass  were  im- 
permeable. Some  of  the  specimens  composed  of  1-2  mortar  in 
the  proportions  of  40  and  45  per  cent,  were  also  impermeable, 
as  well  as  the  1-2-4  an<3  1-2^-4  mixtures.  All  other  mixtures 
leaked  at  the  high  pressure  (80  Ibs.  per  sq.  in.)  and  in  a  gen- 
eral way  exhibited  a  degree  of  imperviousness  in  direct  pro- 


WATERPROOFING    CONCRETE.  669 

porti'on  to  the  proportion  of  mortar  in  them,  with  the  lower 
pressures  from  20  Ibs.  per  sq.  in.  up  as  well  as  for  the  8o-lb. 
pressure. 

Other  tests  confirm  those  cited.  In  general  we  may  con- 
clude that  those  mixtures  richest  in  cement  and  mortar  are 
the  most  impervious.  It  is  doubtless  practicable  by  exercising 
proper  care  to  proportion,  mix  and  place  a  concrete  mixture 
which  will  be  so  nearly  impervious  that  visible  leakage  will  be 
small.  The  task,  however,  is  one  difficult  to  perform  in  actual 
construction  work,  and  its  accomplishment  is  never  certain. 

STAR  STETTIN  CEMENT.— Star  Stettin  cement  is  a 
Portland  cement  made  by  grinding  a  clinker  which  has  been 
"impregnated"  with  substances  which  imparT  waterproofing 
properties  to  the  ground  product.  The  process  is  the  inven- 
tion of  Richard  Liebold,  and  the  cement  is  made  by  the  Star 
Stettin  Portland  Cement  Works,  Stettin,  Germany.  It  is 
asserted  that  a  1-4  fine  sand  mortar  made  with  this  cement  is 
impervious.  To  use  it  the  ordinary  precautions  adopted  in 
the  employment  of  Portland  cement  are  necessary,  and  in 
addition  the  following:  The  cement  must  be  mixed  with 
moist  instead  of  dry  sand  before  the  water  is  added ;  the  sand 
should  be  clean,  sharp  and  fine  of  grain ;  the  mortar  must  be 
more  perfectly  mixed  than  ordinarily,  and  somewhat  more 
water  should  be  used  than  is  ordinarily  used.  Perfectly  even 
mixing  is  essential  to  the  best  results. 

MEDUSA     WATERPROOFING      COMPOUND.— This 

compound  is  a  dry  powder  which  is  mixed  with  the  cement 
in  proportions  of  from  I  per  cent,  to  2  per  cent,  by  weight, 
or  from  4  Ibs.  to  8  Ibs.  per  barrel  of  cement.  The  compound 
costs  12  cts.  per  lb.,  so  that  its  addition  increases  the  cost  from 
48  to  96  cts.  per  barrel  of  cement.  Thorough  mixing  of  the 
compound  with  the  cement  is  of  the  utmost  importance,  other- 
wise none  but  the  ordinary  precautions  in  the  use  of  Portland 
cement  is  necessary.  Absorption  tests  on  concrete  blocks 
treated  and  untreated  with  the  compound  and  nine  months  old 
have  shown  the  absorbtion  of  treated  blocks  to  be  about  one- 
fourth  or  one-fifth  that  of  untreated  blocks.  The  compound  is 
made  by  the  Sandusky  Portland  Cement  Co.,  Sandusky,  Ohio. 


670  CONCRETE    CONSTRUCTION. 

NOVOID      WATERPROOFING      COMPOUND.— This 

compound  is  a  dry  powder  which  is  mixed  dry  with  the 
cement  in  the  proportion  of  I  to  2  per  cent,  by  weight  or  about 
i  to  2  Ibs.  per  bag  of  cement.  The  compound  costs  12  cts.  per 
pound  or  about  from  48  to  96  cts.  per  barrel  of  cement.  Direc- 
tions for  making  waterproofing  mortar  are :  To  100  Ibs.  of 
Portland  cement  add  2  to  2.l/2  Ibs.  of  compound  and  200  Ibs.  of 
clean  and  sharp  sand  and  mix  the  materials  dry  and  very 
thoroughly.  The  water  is  then  added  in  the  proportion  neces- 
sary to  make  a  good  working  mortar  and  the  mortar  mixed 
and  applied  in  the  ordinary  manner.  Used  as  a  wash  2  Ibs.  of 
compound  are  thoroughly  mixed  dry  with  a  bag  of  cement. 
Any  portion  of  the  mixture  is  then  mixed  with  water  to  pro- 
duce a  creamy  grout,  which  is  applied  to  a  thoroughly  wet 
surface  with  a  brush.  This  compound  is  made  by  The  Abbey- 
Dodge-Brooks  Concrete  Co.,  Newark,  N.  J. 

IMPERMEABLE    COATINGS    AND    WASHES.— The 

most  common  means  employed  for  rendering  concrete  struc- 
tures waterproof  is  to  coat  or  wash  the  surface  with  some 
substance  itself  impervious  to  water  or  having  the  property 
of  closing  the  pores  of  the  surface  skin  of  concrete  so  that 
water  cannot  penetrate. 

Bituminous  Coatings. — Bituminous  coatings  of  one  com- 
position or  another  are  among  the  most  commonly  used  of 
impermeable  coatings.  The  bituminous  compound  is  used 
both  alone  and  in  combination  with  layers  of  a  fabric  of  some 
sort  to  form  the  coating.  Where  bituminous  coatings  are  used 
on  surfaces  exposed  to  the  sun  and  frost  attention  must  be 
given  to  the  fact  that  a  compound  of  different  properties  is 
required  where  the  range  of  temperature  is  great  than  is  re- 
quired where  this  range  is  smaller.  Asphalt,  for  example, 
should  have  a  flow  point  of  212°  F.  and  a  brittle  point  of 
— 15°  F.  when  exposed  directly  to  sun  and  frost  as  compared 
with  say  a  flow  point  of  185°  F.  and  a  brittle  point  of  o°  F. 
when  covered  from  the  direct  action  of  sun  and  frost.  An- 
other point  to  be  kept  in  mind  particularly  in  using  exterior 
coatings  is  that  the  concrete  surface  must  be  properly  pre- 


WATERPROOFING    CONCRETE.  671 

pared  to  receive  the  coating  or  else  it  will  peel  off.  The 
following  are  examples  from  actual  practice  of  waterproofing 
with  bituminous  coatings. 

The  following  method  of  waterproofing  with  asphalt  coat- 
ing is  given  by  W.  H.  Finley :  The  asphalt  used  must  be  of 
the  best  grade,  free  from  coal  tar  or  any  of  its  products,  and 
must  not  volatilize  more  than  0.5  per  cent,  under  a  tempera- 
ture of  100°  F.  for  10  hours.  It  must  not  be  affected  by  a  20 
per  cent,  solution  of  ammonia,  a  35  per  cent,  solution  of  hydro- 
chloric acid,  a  25  per  cent,  solution  of  sulphuric  acid,  or  a 
saturated  solution  of  sodium  chloride.  For  structures  under- 
ground a  flow  point  of  185°  F.  and  a  brittle  point  of  o°  F. 
shall  be  required.  If  the  surface  cannot  be  made  dry  and 
warm  it  should  first  be  coated  with  an  asphalt  paint  made  of 
asphalt  reduced  with  naphtha.  The  asphalt  should  be  heated 
in  a  kettle  to  a  temperature  not  exceeding  450°  F.  It  has  been 
cooked  enough  when  a  piece  of  wood  can  be  inserted  and  with- 
drawn without  the  asphalt  clinging  to  it.  The  first  coat 
should  consist  of  a  thin  layer  poured  from  buckets  on  the 
prepared  surface  and  thoroughly  mopped  over.  The  second 
coat  should  consist  of  a  mixture  of  clean  sand  and  screenings, 
free  from  earthy  admixtures,  previously  heated  and  dried,  and 
asphalt,  in  the  proportion  of  I  of  asphalt  to  3  or  4  of  sand 
or  screenings  by  volume.  This  is  to  be  thoroughly  mixed 
in  the  kettle  and  then  spread  out  on  the  surface  with  warm 
smoothing  irons,  such  as  are  used  in  laying  asphalt  streets. 
The  finishing  coat  should  consist  of  pure  hot  asphalt  spread 
thinly  and  evenly  over  the  entire  surface,  and  then  sprinkled 
with  washed  roofing  gravel,  torpedo  sand,  or  stone  screenings, 
to  harden  the  top.  The  thickness  of  the  coating  will  depend 
on  the  character  of  the  work  and  may  vary  from  ^  m-  to  2  ms- 
in  thickness. 

Several  firms  manufacture  and  sell  ready  made  priming 
paints  and  mastics  for  waterproofing  concrete  by  substantially 
the  above  method.  Sarco  compounds  made*  by  the  Standard 
Asphalt  &  Rubber  Co.,  of  Chicago,  111.,  are  examples.  Sarco 
waterproofing  is  a  compound  analyzing  99.7  per  cent,  pure 
bitumen  and  having  a  range  of  ductility  of  200°  F.  In  water- 
proofing large  car  barn  roofs  of  concrete  in  Chicago,  the  con- 


672  CONCRETE    CONSTRUCTION. 

crete  was  first  swept  clean  and  a  coat  of  priming  compound 
was  thoroughly  brushed  in.  On  the  priming  coat  was  mopped 
a  coat  of  waterproofing  compound,  applied  hot,  and  covered 
with  a  layer  of  fine  sand.  The  thickness  of  the  completed 
coating  was  1-16  in.  Where  a  heavier  waterproofing  is  neces- 
sary the  waterproofing  compound  is  covered  with  one  or 
more  ^g-in.  coats  of  Sarco  mastic. 

The  following  bituminous  coatings  have  been  used  in  water- 
proofing concrete  fortifications  by  the  U.  S.  Army  Engineers : 

Mobile,  Ala. — The  top  of  the  concrete  was  covered  with  a 
thin  coat  of  1-2  cement  mortar  and  given  a  rough  trowel 
finish.  As  soon  as  the  surface  was  dry  it  was  covered  with 
a  layer  of  asphalt  mastic  I  in.  thick  and  rubbed  down  to  a 
finish  with  dry  sand  and  cement  in  equal  parts.  To  prepare 
the  mastic  take  500  Ibs.  of  Diamond  T  asphalt  mastic,  broken 
into  small  pieces,  36  Ibs.  of  Diamond  T  asphalt  flux,  and  5 
Ibs.  of  petroleum  residuum  oil.  When  thoroughly  melted  add 
400  Ibs.  clean,  dry  torpedo  gravel  previously  heated.  Stir 
gravel  and  asphalt  until  thoroughly  mixed  at  a  temperature 
of  about  375°  F. 

Key  West,  Fla. — The  top  of  the  concrete  was  covered  with 
smooth  plaster,  proper  slope  for  drainage  being  given.  Above 
this  two  layers  of  asphalt  of  an  aggregate  thickness  of  ^4  m- 
were  applied.  The  composition  of  the  asphalt  was  as  fol- 
lows: 440  Ibs.  rock  asphalt  mastic,  3  gallons  coal  tar,  and 
5  gallons  silicious  sand. 

Delaware  River  Defenses. — The  concrete  was  waterproofed 
with  coal  tar  and  sand.  The  tar  was  made  hot  and  applied 
to  the  surfaces  with  rubber  squeegees  and  then  sanded. 
Joints  were  filled  with  the  hot  tar.  A  surplus  of  sand  was  left 
on  for  a  few  days  and  then  swept  off.  One  barrel  of  coal  tar 
covered  2,279  scl'  ft-  with  one  coat  and  cost  $4.25  per  barrel 
delivered.  The  cost  including  material  and  labor  was  0.74  ct. 
per  sq.  ft. 

San  Francisco  Harbor. — The  roof  had  a  pitch  of  about  3  in 
20  and  was  covered  with  an  earth  fill.  The  concrete  was  trow- 
eled to  a  fairly  smooth  surface,  was  mopped  with  a  heavy  coat 
of  roofing  asphaltum,  or  mastic,  then  covered  with  the  heaviest 
grade  roofing  felt  laid  3  ply,  starting  at  the  coping  of  the 


WATERPROOFING    CONCRETE.  673 

parade  wall  and  made  4  ply  in  the  gutter.  On  this  assumed 
water-tight  surface  3-in.  book  tile  was  laid  with  joints  normal 
to  the  gutter  and  cemented.  The  purpose  of  the  tile  w^s  to 
afford  a  free  passage  for  the  water  as  soon  as  it  met  the  roof. 
The  expectations  were  fully  realized  and  no  water,  or  even  a 
sign  of  moisture,  has  appeared  in  this  battery,  or  at  another 
of  the  same  type  since  built,  after  a  fair  test  of  time. 

The  total  cost  of  the  work,  including  mastic,  felt  and  tile, 
was  17  cts.  per  sq.  ft.  for  6,200  sq.  ft.  covering  three  roofs. 

In  conclusion  it  may  be  noted  that  any  of  the  methods  of 
constructing  impermeable  diaphragms  can  be  used  for  con- 
structing impermeable  coatings. 

Szerelmey  Stone  Liquid  Wash. — This  wash  has  been  used 
in  England  for  waterproofing  and  preserving  masonry  for 
some  20  years.  It  is  a  thin  liquid  compound  which  is  applied 
to  the  surface  with  a  brush.  The  stone  or  concrete  surface  is 
required  to  be  dry  and  thoroughly  clean,,  with  all  scale  and 
loose  particles  removed.  The  standard  treatment  is  three 
coats;  i  gallon  of  liquid  is  in  most  cases  sufficient  for  treat- 
ing (three  coats)  25  sq.  yds.,  but  in  exceptionally  bad  cases 
i  gallon  for  15  sq.  yds.  has  been  found  necessary.  The  pre- 
cautions necessary  for  the  successful  use  of  the  liquid  are:  It 
must  be  well  stirred ;  it  must  be  applied  to  a  perfectly  dry, 
clean  surface,  and  it  must  be  well  rubbed  into  the  masonry. 
The  American  agency  for  the  liquid  is  Szerelmey  &  Co.,  Wash- 
ington, D.  C. 

Sylvester  Wash. — Waterproofing  with  Sylvester  wash  con- 
sists in  applying  alternately  to  the  concrete  surface  a  soap 
solution  wash  and  an  alum  solution  wash.  The  soap  solution 
is  applied  first,  and  it  must  be  applied  hot  and  to  a  dry  sur- 
face; the  alum  solution  is  applied  second  and  24  hours  after 
the  soap  solution  and  is  applied  cold.  This  constitutes  one 
treatment.  After  24  hours  a  second  treatment  may  be  given, 
and  as  many  treatments  may  be  given  as  necessary.  In  some 
cases  as  many  as  six  treatments  have  been  employed.  The 
proportions  of  the  solutions  used  in  practice  vary.  In  water- 
proofing the  standpipe  described  in  Chapter  XXII  the  soap 
solution  consisted  of  12  oz.  pure  Castile  olive  oil  soap  per 
gallon  of  water,  and  the  alum  solution  consisted  of  2  oz.  of 


674  CONCRETE    CONSTRUCTION. 

»  • 

alum  per  gallon  of  water.  In  repairing  the  bottom  of  a  reser 
voir  lined  with  4  to  6  ins.  of  concrete  the  following  solutions 
were  used :  24  Mb.  Olean  soap  to  I  gallon  of  water  and  l/2  lb. 
alum  to  4  gallons  of  water.  Both  alum  and  soap  were  well 
dissolved  and  the  soap  solution  was  boiled.  The  boiling  hot 
soap  solution  was  applied  on  the  clean,  dry  concrete;  24  hours 
later  the  alum  wash  was  applied  cold.  This  treatment  was 
repeated  after  24  hours.  Two  men  applied  the  solutions,  using 
whitewash  brushes,  while  a  third  man  carried  pails  of  the 
solution.  In  making  the  soap  solution  two  men  attended  fo'ur 
kettles,  one  man  kept  up  fires,  two  men  carried  solution  to 
men  applying  it.  The  alum  solution  required  fewer  men,  being 
made  cold  in  barrels.  After  applying  the  second  «oap  wash 
to  the  concrete  slopes,  the  men  had  to  be  held  by  ropes  to 
keep  from  slipping.  The  rope  was  placed  around  two  men, 
who  started  work  at  the  top  of  the  slope,  a  third  man  paying- 
out  the  rope.  The  work  was  done  in  8l/2  days  and  cost  as 
follows : 
Labor : 

1,140  hours  labor  at   15   cts $171.00 

83  hours  foreman  at  30  cts 24.90 

83  hours  waterboy  at  6  cts 4.98 

Add  for  superintendence  15% 30.13 


Total  labor $231.01 

Materials : 

900  Ibs.  Olean  soap  at  4  1-3  cts $  39.00 

210  Ibs.  alum  at  3  cts 6.30 

6  lo-in.   whitewash   brushes   at   $2.25 13-S° 

6  stable  brushes  at  $1.25 7.50 

Total   materials $  66.30 

Total  labor  and  materials $297.31 

This  covered  131,634  sq.  ft.,  hence  the  cost  of  the  two  coats 
of  soap  and  alum  was  $2.26  per  1,000  sq.  ft.,  or  0.23  ct.  per 
sq.  ft. 

The  ordinary  Sylvester  wash,  as  described  above,  has  been 
modified  with  success  on  Government  fortification  work  as 
follows ;  To  2  gals,  of  water  add  i  lb.  concentrated  lye  and 


WATERPROOFING    CONCRETE.  675 

5  Ibs.  alum  and  mix  until  completely  dissolved.  This  is  a 
concentrated  stock  solution.  In  use  I  pt.  of  solution  and  10  Ibs. 
of  cement  are  mixed  with  enough  water  to  make  a  mixture 
that  will  lather  freely  under  the  brush.  Two  coats  of  this 
wash  are  applied,  the  second  at  any  time  after  the  first  is  dry, 
and  the  first  as  soon  as  the  forms  are  removed  from  the  con- 
crete. The  wash  should  be  applied  to  a  wet  surface,  if  the  con- 
crete is  dry  it  should  be  wet  down  with  a  brush  ahead  of  the 
wash. 

Sylvester  Mortars. — In  this  class  of  coatings  the  alum  and 
soap  are  added  to  the  mortar  which  is  used  for  facing.  A  suc- 
cessful recipe  for  such  a  mortar  is  given  as  follows :  To  I  part 
ceme-it  and  2  parts  sand  add  3/4  Ib.  of  pulverized  alum  for  each 
cubic  foot  of  sand  and  mix  these  ingredients  dry;  then  add 
the  proper  quantity  of  water,  in  which  has  been  dissolved 
Y^  lb.  of  soap  to  the  gallon,  and  mix  the  mortar  thoroughly. 
Such  a  mortar  is  but  slightly  inferior  in  strength  to  ordinary 
mortar  of  the  same  proportions.  In  plastering  a  clear  water 
well  to  prevent  leaking  a  1-2  mortar  was  made  as  follows: 
il/4  Ibs.  of  soap  were  dissolved  in  15  gallons  of  water  and 
3  Ibs.  of  powdered  alum  were  mixed  with  i  bag  of  cement. 
Two  coats  of  plaster  of  an  aggregate  thickness  of  l/>  in.  were 
applied  and  completely  stopped  the  leaking.  The  cost  of  this 
treatment  was  as  follows : 

2  Ibs.  soap  (with  24  gals,  water)  at  Jl/2  cts $0.15 

12  Ibs.  alum  at  3^2  cts , 0.42 

Total  per  barrel  of  cement $0.57 

In  lining  a  new  reservoir  near  Wilmerding,  Pa.,  a  mortar 
was  made  as  follows :  A  stock  solution  of  2  Ibs.  caustic  potash 
and  5  Ibs.  alum  to  10  quarts  of  water  was  made  in  barrel  lots, 
from  which  3  quarts  were  taken  for  each  batch  of  2  bags  of 
cement  and  4  bags  of  sand.  A  batch  of  mortar  covered  an  area 
6x8  ft.  with  a  i-in.  coat.  The  extra  cost  of  the  water- 
proofing was : 


676  CONCRETE    CONSTRUCTION. 

loo  Ibs.  caustic 'potash  at  10  cts $10.00 

70  Ibs.  caustic  potash  at  9  cts 6. 30 

960  Ibs.  alum  at  3^,  3^4  and  4  cts 34-38 

60  hours  mixing  at  15  cts 9.00 

Freight,  express  and  haulage 11.50 

Total  for  74,800  sq.  ft.. $71.18 

This  gives  a  cost  of  95  cts.  per  1,000  sq.  ft.,  or  less  than 
o.i  ct.  per  sq.  ft.  It  was  found  that  if  less  than  2  parts  of  sand 
to  i  part  of  cement  was  used  the  mortar  cracked  badly  in 
setting.  Clean  sand  was  imperative,  as  any  organic  impurities 
soon  decomposed,  leaving  soft  spots.  Do  not  use  an  "excess  of 
potash;  a  slight  excess  of  alum,  however,  does  not  decrease 
the  strength  of  the  mortar. 

Hydrolithic  Coating.—  This  waterproofing  is  a  dry  mortar 
composed  by  mixing  a  cementing  compound  with  sand,  and 
sold  dry  in  sacks  containing  96  Ibs.  each.  The  dry  mortar  is 
mixed  with  water  to  proper  consistency  for  plastering,  and  is 
applied  as  a  plaster  to  the  surfaces  to  be  waterproofed.  The 
dry  mortar  is  mixed  with  water  to  a  grout  of  the  consistency 
of  thick  cream  and  then  this  grout  is  stiffened  to  the  proper 
consistency  by  adding  more  dry  mortar.  Thoroughness  of 
mixing  is  absolutely  essential.  The  concrete  surface  is  pre- 
pared by  picking  and  scoring  sufficiently  to  get  a  fresh  sur- 
face and  washing  away  all  chips,  dust  and  loose  material,  or 
instead  of  picking  in  new  work  the  outer  skin  may  be  removed 
by  a  i  to  9  muriatic  acid  solution  and  then  washed  free  of  all 
acid  and  scrubbed  with  wire  brushes.  After  preparing  the 
fresh  surface  it  is  well  wetted;  in  fact  water  soaked,  so  that, 
while  not  oozing  moisture  it  will  absorb  no  more  water.  The 
mixed  mortar  is  then  applied  with  a  trowel  in  a  workmanlike 
manner.  In  mixing,  no  more  than  8  gallons  of  water  per  bar- 
rel of  mortar  should  be  used.  The  coatings  used  are  y%  to  y$ 
in.  for  walls  and  y>  to  Y\  in.  for  floors.  The  following  estimate 
of  cost  is  made  by  the  manufacturers,  the  E.  J.  Winslow  Co.. 
Chicago,  111.  The  figures  are  presented  with  the  understand- 
ing that  they  are  to  be  considered  merely  as  average  costs 
for  waterproofing,  without  special  construction,  and  subject 


WATERPROOFING    CONCRETE. 

to  change  in  accordance  with  local  conditions,  and  to  the  time 
of  year  when  the  work  will  need  to  be  performed : 

Per  sq.  ft. 
To  prepare  surfaces  to  receive  "coating"  may  cost  the 

contractor  ^y2  c±St 

The  coating  material,  f.  o.  b.  Chicago,  may  cost  the 

contractor 41^  cts> 

The  labor  of  application  may  cost  the  contractor. ..  .  7^  cts. 
Administration  and  incidental  expenses  may  cost  the 

contractor    .......  0 *jy2  cts. 

25  cts. 

The  lowest  price  yet  asked  for  work  was  20  cts.,  and  the 
highest,  55  cts.,  these  two  prices  representing  the  opposite 
extremes  of  conditions  that  different  jobs  will  present. 

Cement  Mortar  Coatings. — Rich  cement  mortar  mixtures 
offer  considerable  resistance  to  penetration  by  water  and  when 
well  made  may  be  used  with  a  fair  degree  of  success  to  water- 
proof ordinary  concrete.  European  engineers  make  wide  use 
of  mortar  coatings  for  waterproofing  tanks  and  reservoirs  and 
appear  to  have  good  success  with  them.  The  experience  in 
this  country  is  that  no  great  reliance  can  be  placed  on  them, 
where  the  pressures  are  at  all  large.  Records  of  work  done 
show  both  successes  and  failures,  with  no  apparent  reason 
for  either  so  far  as  composition  of  mortar  or  quality  of  work- 
manship goes.  A  rich  mortar  plaster  will  reduce  leakage,  and 
may  prevent  it  entirely,  but  it  is  uncertain  how  far  it  will 
prove  water  tight. 

Oil  and  Paraffin  Washes. — The  theory  of  the  use  of  oil  and 
paraffin  washes  is  that  the  material  soaks  into  the  concrete  and 
closes  the  surface  pores  against  the  penetration  of  water. 
Paraffin  has  been  quite  widely  used  for  preserving  stone 
masonry  walls  for  buildings.  It  is  applied  hot,  and  jn  the  best 
practice  is  applied  to  a  dry  heated  surface.  Concerns  doing 
such  work  on  buildings  have  portable  devices  for  heating  the 
masonry.  Oil  is  sometimes  applied  hot  but  is  more  often 
flushed  onto  the  surface  and  allowed  to  soak  in  as  it  will. 


678  CONCRETE    CONSTRUCTION. 

IMPERMEABLE  DIAPHRAGMS.— The  most  generally 
employed  method  of  waterproofing  concrete  structures,  with 
the  possible  exception  of  painting  and  coating  methods,  is  to 
embed  in  the  wall,  roof  and  floor  slabs  a  diaphragm  that  is  im- 
pervious to  water.  Such  diaphragms  are  usually  composed  of 
layers  of  waterproof  felt  or  paper  cemented  together  and  to 
the  concrete  by  asphalt,  coal  tar  pitch  or  patented  cementing 
compound.  Another  construction  consists  of  a  layer  of 
asphaltic  compound  between  two  layers  of  cement  mortar.  In 
some  cases  also  the  combination  felt  and  cementing  compound 
diaphragm  is  further  strengthened  by  placing  it  between  layers 
of  mortar.  In  wall  work  the  diaphragm  is  frequently  applied 
to  the  face  of  a  single  layer  brick  wall  and  the  .concrete  filled 
against  it.  The  brick  wall  may  be  further  waterproofed  by 
laying  the  brick  in  hot  asphalt  instead  of  in  mortar. 

Within  the  last  few  years  a  number  of  firms  have  devoted 
their  efforts  to  producing  special  fabrics  (felts  or  papers)  and 
special  cementing  compounds  designed  to  be  used  with  the 
fabrics  for  waterproofing  concrete.  These  fabrics  and  cements 
are  in  most  cases  superior  in  toughness,  flexibility,  ease  of 
application,  etc.,  to  the  ordinary  roofing  and  waterproofing 
fabrics  designed  originally  for  general  building  purposes. 

Long  Island  R.  R.  Subway. — In  constructing  the  Long 
Island  R.  R.  subway  the  roof  was  waterproofed  according  to 
specifications  as  follows :  After  the  roof  concrete  \vas 
crowned,  brought  to  a  smooth  surface  and  thoroughly  dried, 
it  was  swabbed  over  with  hot  melted  "medium  hard''  coal  tar 
pitch  to  an  even  thickness  of  not  less  than  1-16  in.  Immedi- 
ately upon  the  first  coat  of  pitch  and  while  it  was  still  melted 
was  laid  a  covering  of  single-ply  roofing  felt,  with  the  sheets 
lapping  4  ins.  on  all  cross  joints  and  12  ins.  on  longitudinal 
joints.  This  felt  was  in  turn  mopped  with  pitch,  and  upon 
that  again  was  laid  another  layer  of  roofing  felt,  which  was 
given  a  final  coating  of  pitch.  The  pitch  used  was  of  a  grade 
somewhat  softer  than  that  used  for  roofing  purposes,  or  such 
as  would  soften  at  a  temperature  of  60°  F.  and  melt  at  a 
temperature  of  100°  F.  The  felt  used  consisted  of  pure  wood 
paper  pulp  or  asbestos  pulp,  which  had  been  thoroughly 


WATERPROOFING    CONCRETE.  679 

treated  and  soaked  in  refined  coal  tar  and  which  weighed  for 
single  ply  at  least  15  Ibs.  per  100  sq.  ft. 

After  the  waterproofing  with  pitch  and  felt  had  thoroughly 
hardened  it  was  plastered  over  with  a  trowel  with  a  i-in. 
layer  of  Portland  cement  mortar,  laid  in  uniform  squares,  in 
every  respect  similar  to  the  plaster  on  top  of  granolithic  pave- 
ment. The  dimensions  of  the  squares  were  5x5  ft.  Their 
purpose  was  to  take  up  expansion  and  contraction  in  the 
coating. 

During  the  year  1903,  there  were  laid  9,056  sq.  yds.  of  the 
waterproofing  described.  The  labor  cost  of  placing  the  two 
layers  of  felt  and  the  three  coats  of  pitch  was  as  follows:  206 
days  labor  at  a  cost  of  $498  (or  an  average  of  $241  per  day) 
for  the  9.056  sq.  yds.,  which  is  equivalent  to  $l/2  cts.  per  sq. 
yd.  for  labor.  Since  this  is  for  two  layers  of  felt  the  labor 
cost  was  2^4  cts.  per  sq.  yd.  of  single  layer.  The  labor  cost  of 
mixing  and  placing  the  i-in.  mortar  covering  \vas  as  follows: 
It  required  589  days  at  a  cost  of  $1,306  (or  an  average  of 
$2.22  per  day)  to  place  9,056  sq.  yds,,  which  is  equivalent  to 
14/^2  cts.  per  sq.  yd.  The  total  cost  of  labor  for  two  layers 
of  tar  felt  and  the  layer  of  cement  mortar  was,  therefore, 
20  cts.  per  sq.  yd. 

New  York  Rapid  Transit  Subway. — The  waterproofing  con- 
sisted of  alternate  layers  of  asbestos  felt  and  asphalt  laid  on 
the  concrete  and  covered  with  concrete.  A  coat  of  hot  asphalt 
was  laid  on  the  concrete  and  on  this  a  layer  of  felt,  then 
another  coat  of  asphalt  and  another  layer  of  felt,  and  so  on 
until  the  required  number  of  layers  of  felt,  from  2  to  6,  were 
laid  with  asphalt  between  and  on  top  and  bottom.  Natural 
asphalt  containing  not  less  than  95  per  cent,  bitumen  was 
specified.  The  felt  was  required  to  weigh  10  Ibs.  per  100  sq. 
ft.  In  constructing  sidewalls  the  alternative  was  allowed  of 
placing  the  waterproofing  layer  between  a  4-in.  outside  wall  of 
brick  laid  in  asphalt  and  the  concrete  lining.  On  two  sections 
of  the  work  the  actual  cost  of  waterproofing  was  as  follows : 


680  CONCRETE    CONSTRUCTION. 

98,074  sq.  yds.  Single-Ply  Felt.  Per  sq.  yd. 

Labor  laying $0.05 

Materials  and  plant    o.io 

Total $0.15 

1,337  cu.  yds.  Brick  in  Asphalt:  Per  cu.  yd. 

Labor   laying *..-.,.._._.    $  6.32 

Materials  and  plant 1 1 .48 

Total $17.80 


INDEX. 


Page 

Abutment    Construction 
Cost    of 

Bridges  Over  City  Streets.254 
Ernst    St.    Bridge,    Cincin- 
nati,    O 257 

Kansas  City  Outer  Belt  & 

Electric     Ry 253 

Lonesome  Valley  Viaduct.256 

Railway   Bridge    106 

Methods    of 

Bridges  over  City  Streets.253 
Illinois         &         Mississippi 

Canal    196,    197 

Lonesome       Valley       Via- 
duct      254,    255 

Railway   Bridge    105,  250 

Summary    of    230 

Aggregates 

Balanced,    Value    of 14 

Broken     Stone     13 

Cinders     14 

Cost    of    15 

Gravel     14 

Heating      (See     Heating     Ag- 
gregates) 

Kinds    Used     13 

Measuring,     Methods     of 42 

Open    Box    42,   50 

Trump    Automatic    Meas- 
urer        44 

Quantities    in    Concrete,    Test 

Determinations     192 

Screened      or      Crusher      Run, 

Stone    for    15 

Sizes   Used    15 

Slag    14 

Voids    in    25 

Weighing,     Apparatus     for 102 

Aqueduct     Construction 
Cost   of 

Cedar         Grove          Reser- 
voir      549,550 

Salt        River          Irrigation 

Work     540 

Methods   of 

Cast   Pipe   Swansea,   Eng- 
land      584 

Cedar    Grove    Reservoir.  ..545 

Jersey    City    Water    Sup- 
ply      544 

Salt         River         Irrigation 
Works     538 

Torresdale    Filters    540 

Asphalt    Concrete 

Definition   of    108 

Furnace     for    Heating 109,110 

Machine    Mixing    of HI 

Asphalt    Concrete    Construction 
Cost    of 

Base    for   Mill  Floor..  110,  111 

681 


Page 

Asphalt  Concrete  Construction 
Cost  of 

Slope    Paving    for    Darrt..l09 
Methods   of 

Base    for   Mill    Floor 109 

Slope    Paving   for   Dam... 
108,.  109 


B 

Bags  (See  Cement  Bags) 

Depositing      Concrete      Under 

Water    89,    90 

'Barrels   (See  Cement  Barrels) 
Belt  Conveyors 

Capacity   of    65 

Gas    Works    Foundations,    As- 
toria,  N.  Y 64 

Horse    Power    Required 65 

Bench  Monuments 

Construction  of    656 

Cost    of    657 

Blasting    Concrete 655 

Bonding   New    Concrete   to   Old... 659 
Breakwater  Construction 
Cost    of 

Buffalo,   N.    Y 214 

Marquette,   Mich 209.  212 

Methods    of 

Buffalo,   N.   Y 212,  214 

Marquette,  Mich.    .    ..208,  212 
Bridge  Centers    (See   Centers) 
Bridge  Construction 
Cost    of 

Arch   Viaduct    3(3 

Connecticut     Ave.     Bridge 

392,     397 

Elkhart,    Ind.,    Arch 398 

Five  Span  Arch 40  < 

Girder    Highway     ....3,7,  379 
Grand    Rapids    Bridge.410,  413 

Molded   Slab   Girders 387 

Plainwell.    Mich.,    Arch.... 399 

Railway    Bridge    37o 

Methods  of 

Connecticut   Ave.   -Bridge.. 38 » 

Elkhart,     Ind..     Arch 39< 

Five  Span  Arch   V«V'I28 

Girder    Highway     36 1.  3  <  7 

Grand        Rapids.        Mich., 

Arch     407 

Molded    Slab  Girders 384 

Plainwell,    Mich-.,    Arch...  398 
Bridge    Pier  Construction 

°S  Calf    Killer    River    Briclge^_ 

City'  'island'  Bridge.  .T. .'.  .236 

Miami     River     Bridge 25  < 

Steel    Cylinder     241 


682 


INDEX. 


Page 

Bridge    Pier    Construction 
Cost   of 

Viaducts.    Cincinnati,    U.  ..258 
Williamsburg    Bridge. 230,  231 
Methods    of 

Calf    Killer    River    Bridge 

2-1],     245 

City    Island    Bridge 235 

K.    C.,    M.    &    O.    Ry..24~>,  250 
Lonesome      Valley  *      Via- 
duct     254,    255 

Miami    River    Bridge 256 

Nova     Scotia     Railways. .  .108 

Railway    Bridge    231,235 

Scottish     Railways     ..107,  108 

Summary    of     230 

Tharsis  &   Calamas  Ry... 

106,     107 

Williamsburg     Bridge.237,  241 

Broken   Stone 

Crushing     (See     Stone    Crush- 
ing) 
Quarrying    (See    Quarrying) 

Rocks    for,     Best 13 

Shoveling     (See     Shoveling) 
Screened    or    Crusher    .Run....    15 
Voids   in 

Amount   of    20,30 

Effect     of      Granulometric 

Composition    3') 

Effect    of   Hauling 33,  34 

Effect    of    Loading 2.) 

Variation,    Causes    of 28 

Weight    no    Index 32 

Weight   of    32,  33 

Building    Construction 
Cost   of 

Four-Story    Garage    510 

Wall    Columns    for    Power 

Station     400 

Walls    for    Factory   Build- 
ing      r,07 

Divisions   of   Work 433 

Methods    of 

Four-Story    Garage    509 

One-Story    Car  Barn 495 

Six-Story    Building     431 

Wall  Columns    488 

Walls    for   Factory    Build- 
ing     505 


Cableways 

Capacity    of    64 

Construction  of  Bridge  Work. 369 

Cost    of    64 

Fortification    Work     186 

Retaining    Wall    Work 269 

Cars 

Mixer  Charging   72 

Carts   (See   Concrete  Carts.  Horse 

Carts) 
Cement 

Classification    of    1 

Natural   Definition    of 2 

Portland,    Definition    of 1 

Quantity  in  Concrete 

Formula    for    Computing..   37 

Rule  for  Figuring   40 

Tables  Showing   39,  40,  41 

Quantity    in    Mortar 

Formula    for   Computing..   36 

Tables  Showing   38 

Test    Determinations    ..40,  41 
Theory    of    35 


Page 

Cement 

Shrinkage   by   Wetting 35 

Slag,    Definition    of    2 

Weight    2,   4 

Cement    Bags 

Capa  city   of    2 

Packing    for    Shipment 3 

Rebate    on    3 

Storage  House   for 3 

Cement    Barrels 

Capacity   of    2,    3,    4 

Dimensions  of  4 

Cement    Specifications 4 

Cement    Testing,    Cost    of     4 

Centers 

Computation   of 

Luten  Arch    = .  566 

Construction    uf 

Conditions    Governing     ...363 

Cocket,   50  ft.   Span 364 

Connecticut    Ave.     Bridge. 392 

Five    Span    Arch 400 

Grand     Rapids     Bridge 408 

Luten  Arch    365 

Mechanicsville    Bridge    ...365 

Parabolic    Arch    366 

Supported,     50    ft.     Span.. 364 

Walnut   Lane  Bridge 368 

Cost  of 

Connecticut     Ave.     Bridge 

392,     393 

Deflection*  of 

Test     Determinations     ...367 
Types    of    363 

Charging  Barrows 

Ransome,  Description    71 

Sterling,    Description    71 

Charging  Buckets 

Wheeled     74 

Charging  Mixer 

Cost    of    270.    272 

Gravity    from    Bins 69 

Methods   of 

Car  Plants    72 

Charging    Barrows    70,   71 

Derricks    and    Buckets....   73 
Elevating    Charging    Hop- 
pers    70 

Enumeration    68 

Gravity     from     Bins..., 68,   69 

Shoveling    72,   73 

Wheelbarrows    70 

Wheeled    Bucket     for 74 

Chutes 

Cement    Bag,    Construction    of  65 
Concrete.    Examples    of .  .66,  67,  68 

Working  Gradients    65,  66 

Cinders     15 

Cofferdam  Construction 

Cost    of   Bridge    Pier 232 

Coloring  Concrete.  Recipes  for.. 666 
Colors  for  Mortar,  Recipes  for.  .666 
Concrete 

Asphalt      (See      Asphalt     Con- 
crete) 

Definition   of    l 

Depositing       (See      Depositing 

Concrete) 

Mixers     (See     Mixers) 
Mixing   (See  Mixing  Concrete) 
Proportioning,    Methods    of . . .  25 


INDEX. 


683 


Page 

Concrete   Bucket 

Side    Dumping    486 

Subaqueous 

Cyclopean    87 

O'  Rourke     86 

Stuebner    88 

Concrete  Block 

Molding    (See    Molding      Con- 
crete  Blocks) 

Sling  for  Handling  216 

Concrete  Cars 

Lock    Work,    Coosa    River 195 

Concrete  Carts 

Hand,   Capacity  of 53,  54 

Horse,    Briggs     298 

Ransome  Two- Wheeled 53 

Culvert    Construction 

Characteristics  of   414 

Cost    of 

Arch    26    ft.    Span 425 

Arch,     N.,     C.     &     St.     L. 

Ry 418,    419,    422 

Kalamazoo,    Mich 430 

Kansas     City     Outer     Belt 

&    Electric    Ry 252 

Pennsylvania    R.    R 424 

Methods  of 

Arch,  N.,   C.   &    St.    L.    Ry.417 

Arch,     Wabash    Ry 422 

Box,  C.,  B.  &  Q.   R.  R 414 

Kalamazoo,   Mich 427 

Pennsylvania    R.    R 423 

Curb  and  Gutter  Construction 
Cost  of 

Champaign,    111 326 

Estimating     321 

Ottawa.   Ont 324 

Methods    of 

Champaign,   111 325 

General  Discussion   321 

Kinds   of    31. S 

Ottawa,    Ont 321 

Curbing,  Wood  for  Shafts: ..  .160,  161 


Dam   Construction 
Cost  of 

Hemet    104 

Richmond,    Ind 22  I 

Rock  Island,  111 225 

Spier  Falls   103 

Methods    of 

Barossa   Dam    101 

Boonton,  N.  J.,   Dam 103 

Boyds    Corner   Dam 105 

Chaudiere    Falls,     Quebec.  22S 
Chattahoochee  River  Dam.  100 

Hemet    Dam    103,    104 

McCall    Ferry,    Pa 225,  22S 

Richmond,    Ind 223 

Rock    Island,    111.     ....224,  225 

Spier   Falls   Dam 103 

Water   Works    Reservoir.  .104 
Depositing   Concrete 
Subaqueous 
Bags 

Bridge     Foundations....   91 
Marquette  Breakwater.. 

209,     210 

Peterhead  Pier   89,   90 

Buckets 

Marquette    Breakwater.. 

..208     209 


Depositing  Concrete 
Subaqueous 

Pier  Construction    ...222 

Characteristics  of   86 

Closed  Buckets 86,   87    88 

Tremie 

Charlestown       Bridge 

Foundations    92,93 

Masonry     Bridge    Foun- 
dations,   France    ...93,  91 
Harvard  Bridge  Founda- 
tions        91 

Nussdorf  Lock   Founda- 
tions     94,    95 

Drilling    Concrete.     Drill     Mount- 
ing   for    653 

Dumping   Concrete 
Cost  of 

Wheelbarrows    .55 

Methods  of 

Chutes    55 

Wheelbarrows   55 

Dump    Wagons    for    Transporting 
Concrete 54 


Efflorescence 

Causes    of     126 

Preventing,    Methods   of.. 126,  127 
Removing,    Cost    of 127 

Ejecters    for   Washing    Sand 7 

Erecting    Derrick 

Cost     of    Bridge     Pier 232 

Erecting  Forms 

Derrick   for    501 

Directions  for  Building  Work.  4 60 

Erecting  Molded  Columns 

Cost  of   520 

Methods    of    520 

Erecting  Molded   Roof   Slabs 

Cost    of    522 

Excavating  Cofferdams 

Cost  of 232,  244,   230 


Fabricating    Reinforcement 

Bending  Machine   for   468 

Bending    Tables    for 466 

Methods  of 

Building  Work    464 

Five  Span  Arch   Bridge... 402 
Falseworks  in  Form  Construction.  144 
Finishing  Concrete  Surfaces 
Methods    of 

Acid    Etching   and    Wash- 
ing      133 

Careful  Mixing  and   Plac- 
ing Concrete    125.    126 

Coloring   135 

Form   Construction    ..124,   125 

Grout   Washing    130 

Mortar    Facing    128,  129 

Plastering   128 

Scrubbing  and   Washing.. 

131.  132.  133,  134 

Spading  and   Troweling. . . 

127,    128 

Special  Facing  Mixtures.  .130 

Stuccoing    128 

Tooling   133,  134 

Washed  Gravel  or  Pebble.  134 


684 


INDEX. 


Page 

Form  Construction 
Cost  of 

Aqueduct,     Cedar       Grove 

Reservoir     550 

Arch  Culverts  

418,   419,  422,  425,  430 

Battery    Emplacement 188 

Bridge   Abutment    257 

Bridge  Pier   233.  235,  250 

Bridge    Pier   Work 243 

Building    Work    . . 

493,    496,   501,    503,   507,  511 
Connecticut  Ave.   Bridge.. 

392,     393 

Dam    Rock    Island,    111.... 225 

Effect   of   Design   on 137 

Estimating,   Method  of 

146,    147,   148,    149 

Girder  for  Separate  Cast- 
ing      517 

Girder   Highway    Bridge.. 

377,   380,   382 

Grand    Rapids    Bridge 412 

Guard   Lock,   111.,   &   Miss. 

Canal    201 

Gun   Emplacements    185 

Lock,   Coosa   River 19(5 

Lock,    111.    &    Miss    Canal 

202,    206,   207 

Mortar   Battery   Platform.  1ST 
Permanent     Way       Struc- 
tures   .  . .'. 252 

Piers  for  Taintor  Gates...  198 
Pier  Superior  Entry,   Wis.222 
Reservoir     for    Fire     Pro- 
tection     591,   592,   593 

Retaining  Walls  ....273,  275 
Retaining  Wall  Work. 270,  272 
Slab  and  1-Beam  Floors.. .450 

Subway    Lining    362 

Economics    of    136 

Falseworks  and  Bracing. . 

144,    145 

Methods  of 

Aqueduct,     Cedar       Grove 

Reservoir    546 

Aqueduct    Torresdale'  Fil- 
ters    541 

Arch  Culvert    427 

Arch  Culverts 421 

Blocks  for  Lake   Pier 216 

Blocks  Molded  Under  Wa- 
ter     217-219 

Box    Culverts    417 

Bridge  Piers    255 

Building   Work    492.  495 

Cement    Pipe    Molded      in 

Place    ...577 

Circular   Columns    445 

Columns    434 

Connecticut  Ave.   Bridge.. 392 

Coping  for  Walls 264 

Culvert  Pipe    431 

Curb  and  Gutter.. 319.  321,  323 

Dam  Abutments    196 

Dam,  Rock  Island,  111.... 228 
Five  Span  Arch  Bridge . .  400 

Gasholder  Tank   612 

Girder  for  Separate  Cast- 
ing      516 

Guard    Lock,    111.    &    Miss. 

Canal     200 

Lock,    Coosa    River    195 

Lock,    111.    &    Miss.    Canal 
201,    20,3 


Page 

Form    Construction 
Methods  of 

Manhole    Hartford,     Conn.536 

Marquette    Breakwater 

211,    212 

Ornamental  Columns. 446,  447 
Piers  for  Taintor  Gates..  198 
Polygonal  Columns. .  .443,  444 
Rectangular  Columns. . . . 

435,   443,  490,   492,   511 

Reservoir  Bloomington,  111.605 
Reservoir,  Ft.  Meade,  S. 

Dak 600 

Retaining   Wall,    C..    B.    & 

Q.   R.    R 262 

Retaining    Wall,     Chicago 

Drainage  Canal    275 

Retaining       Wall,       Grand 

Central    Terminal    281 

Retaining  Walls,   N.   Y.   C 

&    H.    R.    R.     R 261,  262 

Salt   River  Aqueduct 539 

Sewer,    Cleveland,    0 564 

Sewer     Invert,     Haverhill, 

Mass 554 

Sewer,      Invert,      Medford, 

Mass 535 

Sewer,  Invert,  Middlesbor- 

ough,   Ky. 561 

Sewer,  South  Bend,  Ind.  .551 
Sewer,  Wilmington,  Del.. 572 

Sidewalks    309 

Six-Story  Building   492 

Slab   and   Girder   Floors. . . 

450,   456.  492 

Slab    and    I-Beam    Floors 

448,     450 

Slab  Girders 385 

Steel    for    Conduits    533 

Steel,    McCall    Ferry   Dam 

227,    228 

Steel   Sheathed  Collapsible 

for   Conduits    533 

Tunnel   Centers    

335,    341,   352,   358 

Tunnel    Sidewalls    

330,   335,    340,    351,    358 

Wall 456.   460,   505 

Wall  Columns  for  Factory.  498 
Computation,  Methods  of.  140,  141 
Design 

Considerations   in    141 

Details  Entering 142,  143 

Lubrication,    Methods   of 1-14 

Lumber 

Dressing,    Purpose    of 138 

Finish   and   Dimensions... 

138,    139 

Kinds  Suitable   138 

Mortar  Facing 129 

Pile 

Round    179 

Rectangular  Pier 

Cost    of,    Rule    for    Calcu- 
lating       14 

Removing,  Time  of,  Directions 

for    145,    146 

Unit    Construction,      Purposes 

of    143 

Steel,    Opportunity   for   Devel- 
opment     136 

Fortification    Construction 
Cost  of 

Battery  Emplacement   

188,    189,   190 

Gun   Emplacements    185 

Mortar   Battery   Platform.  137 


INDEX. 


68' 


Page 

Fortif cation    Construction 
Methods  of 

Battery   Emplacement 

187,    189 

Gun    Emplacements    185 

Mortar  Battery  Platform.  .186 
Foundation   Construction 
Street    Railway 

Cost  of  Continuous  Mixer.301 
Methods     of       Continuous 

Mixer 300,  301 

Freezing    Weather,    Laying    Con- 
crete in    .  ..112 


Grain  Elevator  Bins 

Construction,   Methods  of 635 

Gravel 

Characteristics  of   14 

Commercial   Sizes   of 22 

Screening  and  Washing  Plants  23 
Screening       (See         Screening 

Gravel) 
Voids   in 

Amount   of    30,    31 

Effect     of     Granulometric 

Composition    29,    30 

Weight    no    Index 32 

Amount    of 31,    32 

Grouting  Under  Water 

Hermitage   Breakwater    96 

Tests   of  Efficiency   of 95 


Heating  Aggregates 

Efficiency   of    114 

Methods   of 

Bridge   Work,    Piano.   111..  118 
Chicago,       Burlington       & 

Quincy  R.  R 118 

Hot  Water  Tanks   120 

Huronian       Power       Co.'s 

Dam    Work    118 

Portable  Combination 

Heater    115 

Stationary  Bin  Outflts.115,  116 

Steam  Box   119 

Steam   Jets    119 

Wachusett  Dam  Work 117 

Water   Power   Plant,    Bill- 
ings, Mont 116,  117 

Hoists 

Gallows,  Frame  and  Horse....  54 

Ransome    476 

Wallace-Lindsmith    474 

Housing  Concrete  Work 
Methods  of 

Chicago,      Burlington        & 

Quincy    R.    R 119 

Dam.  Chaudiere  Falls,  Que- 
bec  120,    121 

Portable   Unit    System   for 
Buildings   122,   123 


Inclines 

Grades  of 


Page 


Laying   Concrete   Blocks 

Cost    of    526,  529 

Loading  Concrete 

Characteristic  Features    53 

Rate   of 53 

Loading    Materials 
Cost  of 

Shoveling    into    Wheelbar- 
rows         47 

Rate   of    6 

Lock  Construction 
Cost    of 

Coosa    River 196 

111.   &   Miss.    Canal... 

200,    202,   205,    207 

Cascades  Canal    

190,   191,   192,   193 

Coosa    River    194,  195 

111.    &    Miss.    Canal... 200,  207 
Lock    Foundation    .  ..207 


M 


Manhole   Construction 
Cost  of 

Rye,    N.   Y... 577 

Methods  of 

Rye,  N.   Y.    . .- 576 

Mixers 
Batch 

Chicago    662 

'Jhicaaro   Improved 

Cube  75,  66'. 

Cropp    661 

Forms    of    75 

Koehring   661' 

Polygon     6»> '. 

Ransome  75,  661 

Rate  of  Output.    83.   M 

Smith    77,    G''2 

Snell    60.) 

Charging   (See   Charging 

Mixers) 
Continuous 

Advanced     660 

Eureka    Automatic 

Feed     78,    660 

Forms    of    78 

Foote     297 

Scheiffler     660 

Efficiency   of 

Rating,    Methods   of 84,    85 

Gravity 

Forms    of    79 

Gilbreth    Trough    80 

Hains,    Fixed    Hopper.. 80,    81 
Mains,    Telescoping 

Hopper     81 

Output 

Conditions   Affecting. .  .83,    84 

Hains    Gravity 83 

Types  of "4 

Mixing   Concrete 
Hand 
Cost   of 
Abutment    Construction ...  197 

Culvert    Work 428,    430 

Fortification    Work    ......189 

Girder    Highway 

Bridge    380,    382 

Lock,    Cascades   Canal 192 


686 


INDEX. 


Page 

Mixing   Concrete 
Hand 
Cost  of 

Marquette  Breakwater 

209,   210,  212 

Retaining  Wall.  Allegheny.284 

Superintendence     57,    58 

Cost   of    52,    59 

Methods   of 
Abutment  Construc- 
tion     196,    197 

Examples   from   Practice..  49 

Fortification    Work     189 

Lock    Foundation    207 

Marquette   Breakwater. ..  .209 
Retaining  Wall,   Alle- 
gheny     283,    284 

Rates  of 50,    51,   52 

Specific   Directions, 

Necessity   51,  52 

Machine 

Cost   of 361,    362     518 


Buffalo     Breakwater. 
Building  Work. 504,  507 


.214 
511 


Dam  Work,   Rock  Is- 
land,   111 225 

Fortification  Work  ..  .190 
Hains  Gravity  Mixer. .  .  83 
Lock,  Cascades  Canal  .193 
Lock,  111.  &  Miss. 

Canal   206,  207 

Pier,   Superior  Entry, 

Wis 222 

Retaining  Wall,  Alle- 
gheny      284 

Retaining    Wall    Work.. 

270,   273,   275 

Methods    of 

Bridge    Abutment    Work 

253,     254 

Building    Work    471 

Fortification    Work    189 

Hains  Gravity  Mixer 

82.     83 

Operations  Enumerated.   61 
Piers  in    Caissons.  .165,    166 
Mixing    Plants 
Construction 

Battery  Emplacement.  187,  188 

Bridge    Construction 

369,  371,  372,  374,  386,  389, 
403. 

Culvert     Work 

..415,  416,  418,  420,  422,  423 
Dam,  McCall  Ferry,  Pa... 226 
Lock,  Cascades  Canal.  190,  191 
Lock  Work,  Coosa  River.  194 
Lock  Work,  111.  &  Miss. 

Canal 198,    199,  204 

Pier  Work,  Superior,  Wis.. 221 
Retaining      Wall,       Grand 

Central    Terminal     277 

Scow,         Port         Colborne 

Harbor    216,    217 

Traveling,  Chaudiere  Falls 

Dam     228 

Traveling,    Chicago    Track 

Elevation     267 

Traveling,     Galveston    Sea 

Wall     268 

Cost  of 

Lock    Work,    111.    &    Miss. 

Canal     199 

Retaining    Walls,    Chicago 

Drainage    Canal    274 

Mixing  Water 

Reducing    Freezing    Point 

Methods    of    .  ...112 


Page 
Mixing   Water 

Reducing  Freezing  Point 

Salt    (Sodium  Chloride) . . .  11?, 
Solutions   for.   Composition 

of    • 113 

Molding  Blocks 

Cost    of ' 524,    528,    530,    531 

Marquette   Breakwater 211 

Connecticut  Ave.   Bridge ..  395 

Separate    Casting    519 

Methods   of    523,    526 

Connecticut  Ave.   Bridge.. 393 
Marquette   Breakwater.  ..  .21 1 
Pier,   Port  Colbourne  Har- 
bor     215 

Separate  Casting   ....513,   515 
Molding  Cement   Pipe 
Cost   of 

Irrigon,    Ore 584 

Ransome    Mold 577,    579 

Methods  of 

Irrigon,     Ore 581 

Ransome    Mold     577 

Molding    Culvert    Pipe 
Cost   of 

Chic.   &   En.    111.    R.    R 432 

Methods  of 

Chic.    &  En.   111.    it.    R 430 

Molding    Girders 
Cost  of 

Separate    Casting    51 D 

Methods  of 

Separate  Casting. 51 3,  514,  515 
Molding   Piles 

Forms   for    (See   Forms) 
Methods  of 

Corrugated    Polygonal 17G 

Round     179 

Plant   Arrangements    for 160 

Cost    of    :,'22 

Molding  Rocf   Slabs 

Methods    of    521 

Mortar   Facing 
Cost  of 

Lock,   111.   &  Miss.   Canal.. 206 
Forms  for .  .129 


N 


Natural  Cement   (See  Cement) 


Ornament    Construction 
Methods  of 

Iron   Molds    644 

Molding    in    Place 647 

Plaster  Molds    , 646 

Sand   Molding    644 

Wooden    Molds     .  ...637 


Pavement   Base   Construction 
Cost  of 

Batch    Mixer    306 

Batch    Mixer   and    Wagon 

Haulage     302 

Brick,     Champaign,    .ill 296 

Continuous    Mixers 

298,   300.   305 


INDEX. 


687 


Pavement  Base  Construction 
Cost  of 

Miscellaneous    Examples.. 

• 294,   295,    296 

New    Orleans     293 

Stone    Block,    New   York.. 292 

Toronto,     Ont 293 

Traction     Mixer     304 

Methods  of 

Batch    Mixer    305 

Batch    Mjxer    and    Wagon 

Haulage    302 

Continuous    Mixers 

297-300,    304 

Hand    Mixing 290 

Machine    Mixing     290,291 

Traction    Mixer    303 

Mixtures    Employed 288 

Organization    for    288 

Stock   Pile   Distribution 289 

Pavement  Construction 
Cost  of 

F9rtiflcation    Work 186 

Richmond,    Ind 318 

Windsor,    Ont 317 

Methods  of 

Richmond,    Ind 318 

Windsor,    Ont 316 

Pier    Construction 
Cost   of 

Lonesome  Valley  Viaduct. 255 
Superior  Entry,  Wis..222,  223 

Taintor  Gates   198 

Methods  of 

Port    Colborne    Harbor 

215-217 

Superior   Entry,   Wis.  .217-223 
Piers    in    Caissons 
Construction   of 

Methods  of    ..  .159-168 

Cost  of    168,    169 

Pile    Construction.      (See    Molding 
Piles,   Pile   Driving.) 
Cost    of 

Ocean   Pier    173,   174 

Raymond  Process.  152,  154,  155 
Methods   of 

Building  Foundation  Work 

174,    175,    178,    179 

Compressed    Process.  158,     159 

Enumeration  of    151 

Molding  in  Forms 

161-170,  J72.  179,  180 

Molding    in    Place 151 

Ocean     Pier 172,     173 

Raymond    Process 152 

Rollirg    Process     181 

Simplex  Process.  155,    156,   157 
Spi  ead    Footing    Process.. 

157,    158 

Track    Scales    , 181 

Pile  Driving 

Conditions    Requisite    for 
Cost  of 

Ocean  Pier    173,    174 

Methods  of 

Corrugated  Polygonal.  177,  178 

Hammer    '..179,   180,   181 

Water  Jetting 172,    177 

Pile  Driving  Caps 177,    178,    180 

Pile    Rolling   Machine 182 

Piles   (See  Molding  Piles) 
Construction 

Compressol  Process. ..  158,  159 

Octagonal    180 

Rolling    Process    181 

Round   Piles 178,    179 


Piles   (See   Molding  Piles) 
Construction 

Spread    Footing    Process.. 

157,    158 

Square   179,  180 

Cost  of 

Rolling    Process 183 

Driving   (See   Pile  Driving) 

Handling.     Sling    for 175 

Raymond 

Construction,     Method    of. 

151.    152 

Cost   of 152,  •154,    155 

Simplex 

Construction,    Methods  of. 

, 155,    156,    157 

Placing  Concrete 
Cost  of 

Bags,  Under  WTater 210 

Belt   Conveyors 275 

Buckets   Under   Water 209 

Buffalo    Breakwater 214 

Car  and   Trestle  Plant 

..196,   201,  202,   206,   207,   244 

Cars    280,  422 

Cars  and  Chute 193 

Cars  and  Derrick 285 

Derricks 192,    233,    235 

Port   Colborne    Harbor. . .  .217 

Pneumatic    Caissons 230 

Retaining  Wall  Work. 270,  272 

Steel    Cylinder    Pier 241 

Subaqueous    Buckets 223 

Wheelbarrows    189,    197 

198,    257,    285,    418,    419.    423 
Methods  of 

Building  Work    486 

Locks    Coosa    River 194 

Pneumatic   Caissons.  .237,   238 

Retaining  Wall  Work 266 

Sewer    Work     537  ' 

Placing   Reinforcement  » 

Cost  of 

Building  Work    494 

Directions   for    470 

Permanent      Way      Struc- 
tures  252 

Pole  Base,  Cost  of 658 

Portland  Cement    (See   Cement) 
Proportioning     Concrete     (See     Con- 
crete) 

Q 

Quarrying 
Cost  of 

Limestone    18,   276 

Trap    Rock 17 

Methods  of 

Limestone   18 

Trap    Rock 17 


Ramming  Concrete  (See  also  Plac- 
ing   Concrete) 

Cost    of    423 

Conditions    Governing 56 

Examples  from  Practice.. 

56,  57 

Pavement  Base 292,  294 

Methods  of 

Piers,      Lonesome      Valley 

Viaduct     255 

Specific  Directions,  Neces- 
sity of   ....' 57 


688 


INDEX. 


Page 

Raymond  Piles   (See  Piles) 
Reinforcement 

Weight  in  Concrete 

Tables    for    .Estimating... 

663-665 

Removing  Forms 

Derrick    for    502 

Methods  of 

Building  Work   461 

Time    for 

Building    Work    462 

Reservoir     Construction 
Cost  of 

Covered    for    Fire    Protec- 
tion     594,   f>95 

Ft.    Meade,    S.    Dak 601 

Methods  of 

Bloomington,    111 603 

Covered    for    Fire    Protec- 
tion      588 

Fort   Meade,    S.   Dak 597 

Reservoir  Lining 
Cost  of 

Canton,    111 

Chelsea,   Mass 

Jerome   Park 

Pittsburg,  Pa 

Quincy,    Mass 

Methods  of 

Chelsea,   Mass 

Jerome    Park 

Quincy,   Ma'ss 

Reservoir  Roof,   Cost  of 


629 
623 
628 
630 
619 

620 
628 
617 

632 


286 

277 
283 
280 

2N2 


281 
270 


261 


Retaining  Wall   Construction 

Cost    of    

Chicago   Drainage   Canal . 
273- 

Footing    for    Masonry 

Grand   Central    Terminal. 

Railway    Yard 

Methods  of 

Allegheny      Track     Eleva- 
tion     

Chicago  Drainage   Canal., 
272 

Grand    Central    Terminal 
277- 

Subway  in  Trench 269, 

R(  taining   Walls 

Comparison  of  Plain   and   Re- 
inforced    260, 

Types   of    


Rubble    Concrete   Construction 

Cement,    Saving  in 98 

Cost  of 

Abutment,  Railway  Bridgel06 

Hemet   Dam    104 

Spier  Falls  Dam 103 

Economy,    Limitations    to.. 98,    99 

Methods  of 

Abutment,   RailwayBridge.105 

Barossa  Dam 101 

Boonton    Dam 103 

Bridge  Piers,  Nova  Scotia.  108 

Bridge  Piers,   Scotland 

107,    108 

Bridge  Piers,  Spain..  106,  107 
Chattahoochee  River  Dam.  100 
Dams  for  Waterworks. . . . 

104,    105 

Hemet  Dam 103,   104 

Spier    Falls    Dam 103 


Page 

Rubble    Concrete    Construction 

Percentages  Rubble  Stone 

100,    101,    103,    105,    108 

Shape   of   Stones    for 99 

Runway  Construction,  Methods  of.  48 

S 

Salt 

Percentages  in  Mixing  Water.  114 
Sand 

Balanced,    Value   of 6 

Cleanness,    Value    of 5 

Cost   of 

Excavating  and  Loading..     6 

Granulometric  Composition 28 

Prices    Charged    for 6 

Sharpness,    Value    of 5 

Substitutes  for   5 

Voids  in 

Amount    of 26,    28 

Conditions    Affecting 25 

Effect    of  Moisture 25 

Effect  of  Size  of  Grains..  27 

Volume    in    Concrete 5 

Weight   of 6,    26 

Sand  Washing 

Cost  of 

Ejector    Method 10 

Hose  Method   7 

Tank  Method    13 

Methods  of 

Ejectors     7 

Hose    7 

Tank    30 

Rate   of 

Ejector  Method    9 

Hose     Method 7 

Tank  Method 10,  12,   13 

Water  Required 

Ejector  Method    9 

Sand  Washing  Plants 7-13 

Screening  Gravel 

Cost  of 

L.   S.  &  M.   S.    Ry 22 

Stewart-Peck  Sand  Co 24 

Methods   of 

Handwork   19 

Lock.    Cascades    Canal 191 

Scraper   into   Wagons 21 

Stewart-Peck  Sand  Co 23 

Sewer   Construction 

Cost  of 

Cleveland,  0 566 

Coldwater,  Mich 574 

Haverhill,    Mass 557 

Medford,    Mass 535 

Middlesborough,   Ky 562 

St.    Louis,    Mo 560,    561 

South  Bend,  Ind 554 

Wilmington,    Del 571,    573 

Methods  of 

Cleveland,    O 563 

Coldwater,  Mich 573 

Haverhill  Mass 554 

Medford,    Mass . .  535 

Middlesborough,   Ky.    561 

Pipe,  St.  Joseph,  Mo 579 

St.     Louis,    Mo 558 

South    Bend,    Ind 551 

Wilmington,    Del 569 

Shoveling 

Cost  of 

Concrete  into  Barrows 197 

Rate  of 

Broken    Stone   from  Piles.   46 


INDEX. 


689 


Page 
Sh  'iveiing 

Broken   Stone  from    Shov- 
eling  Boards    46 

,  Broken   Stone  from  Cars..   45 
Gravel  Against   Screens...   21 
Sand  into  Wheelbarrows..    46 
Shoveling  Boards 

Wooden,    for   Broken   Stone...   46 
Sidewalk  Construction 
Cost  of 

Estimation    of 311,    312 

Quincy,   Mass 314 

San  Francisco,  Gal 315 

Toronto,    Out 313 

Methods  of 

Bonding   Wearing   Surface 

to  Base   . . .' 310 

Edger  for  310 

General  Discussion   307 

Points  for   310 

Prevention   of  Cracks 311 

Protection   from  Weather. 311 

Quincy,    Mass 314 

Toronto.    Ont 313 

San    Francisco,    Cal 314 

Silo  Construction 

Cost    of    632 

.    Methods    of    631 

Slag    14 

Slag  Cement   (See  Cement) 
Specific  Gravity,   Stone,   Various.. 

32,    33 

Spreading  Concrete 

Cost  of  197 

Effect  of  Method  of  Dump- 
ing on  55 

Standpipe   Construction 
Cost  of 

Attleborough,    Mass 611 

Methods  of 

Attleborough,    Mass 609 

Stock  Piles 

Capacity   of    46 

Distribution.    Pavement  Work.289 

Purposes  of    45 

Stone 

Specific   Gravity    32,    33 

Stone  Crushing 
Cost  of 

Cobblestone    20 

Limestone 18,   225,  273,  276 

Trap   Rock    17 

Methods  of 

Cobblestone     19 

Limestone    18 

Trap    Rock    17 

Stone  Crushing  Plant 
Construction 

Lock    Work.    111.    &    Miss. 
Canal 200 

Stone  Dust,  Value  for  Mortar 5 

Storing  Materials,  Cost  of....  185,  225 
Subway  Lining 
Cost  of 

Long  Island  R.  R 361 

New    York    Rapid    Transit 

Ry. *. 357,  358 

Methods   of 

Long   Island   R.    R 361 

New    York    Rapid    Transit 
Ry 356 


Page 

Superintendence 

Cost  of... 57,   58,    185,   193,    197, 

210,    211,    212,    273,    275,    397 


Tamping  Concrete 

Cost  of  197 

Lock,  111.   &    Miss.   Canal. 

206    207 

Method  of 

Lock,   111.  &   Miss.  Canal.. 204 
Tank  Construction 
Methods  of 

Gas    Holder,    Des    Moines, 

la 609 

Gas  Holder,  New  York 614 

Tooling  Concrete 

Cost   of 394,    396 

Transporting   Concrete 
Cost  of 

Cableways 270 

Cars   280 

Chutes    67 

Cars  and  Derricks 285 

Car  and  Trestle  Plant 

63,  210,  212,  222 

Wheelbarrows 53,    189, 

197,    272,    285,    293,    294,    296 
Methods  of 

Belt    Conveyors    (See   also 

Belt  Conveyors)    64-65 

Bucket  Hoists    474 

Building  Work    472 

Cableways    

64,   180,   289,   369,  370 

Cars 404,    421 

Cars  and  Chute 191   192 

Car   and    Trestle 

63,   243,  246,  377 

Chutes   (see  also  Chutes). 

66.    67,    68 

Derricks    479 

Dump   Wagons    54 

Effect   on   Placing 54 

Enumeration  of   52 

Hand   Costs    53 

Hoist   and    Cars 372 

Platform  Hoists   479 

Pulley   and  Horse 489 

Traveling  Derrick   Plant.. 374 

Trestle  Runways   54 

Wheelbarrows   63 

Transporting  Materials 

Cars    for    45 

Cost  of 

Bridge  Pier  Work 243 

Cars   275 

Car  and  Trestle  Plant 222 

Dam,    Rock   Island,    111 225 

Horse  Carts 49,   270,   273 

Lock,  111.  &  Miss.  Canal.. 

f 206,  207 

Wheelbarrows   

47,    48,    189,    197,    214, 

280,    292,    293.    294,    296,    419 
.  Methods  of 

Belt    Conveyors    (see   also 

Belt  Conveyors)    64-65 

Cableways   64,  269 

Carrying   in    Shovels 47 

Chutes   (see  also  Chutes) . 

46,   65,  66 

Hand   Carts    48 


690 


INDEX. 


Page 
Transporting  Materials 

Horse    Carts    48 

Indians    62 

Shoveling        to        Derrick 

Buckets    46 

Trestle   and    Car    Plants..   63 

Wheelbarrows    47 

Trestle  Runways,  Cost  of 54,   55 

Trestles 

Car,    Cost  of    63 

Structural    Details    G3 

Tunnel    Construction    (See   Tunnel 
Lining) 

Tunnel   Lining 

Backfilling  Machine    for 330 

Cost  of 

Cascade  Tunnel    338 

Gunnison    Tunnel    355 

Hodges  Pass   Tunnel 345 

Mullan   Tunnel    333 

Peekskill    Tunnel     336 

Short    Railway    344 

Methods  of 

Burton    Tunnel     347 

Capitol    Hill,    Washington, 

D.  C 329 

Cascade   Tunnel    336 

General    Discussion    328 

Gunnison    Tunnel    3^3 

Hodges  Pass  Tunnel 338 

Mullan    Tunnel     332 

Peekskill,    N.    Y 333 

Mortar  Car  for 333 

Removing  Old,  Methods  of.... 332 

Traveling    Derrick    for 330 

Traveling  Platform  for... 337,   350 


U 


Unloading  Materials 
Cost  of 

Grab   Buckets 
Methods   of 

Grab    Buckets 


Page 


Voids     (See     also     Gravel,     Sand 
Stone) 
Conditions  Governing    2; 


W 
Wall  Ties 

Construction  of   265 

Washing   Gravel 
Cost  of 

L.    S.    &   M.    S.    Ry 22 

Stewart-Peck   Sand    Co...  24 
Washing   Gravel 
Methods  of 

Lock,    Cascades    Canal 191 

Stewart-Peck  Sand  Co 23 

Water 

Quantity    in   Concrete 

Rule    for    Figuring 42 

Waterproofing 
Cost  of 

Hydrolithic  Coating   677 

Long  Island  R.  R.  Sub  way.  679 

New  York  Subway !.680 

Sylvester  Mortar    675 

Sylvester  Wash  674 

Methods  of 

Bituminous   Coatings 670 

Covered  Reservoir  for  Fire 

Service     59fi 

Hydrolithic   Coatins: 676 

Impervious   Mixtures 668 

Long    Island     R.     R.     Sub- 
way     678 

Medusa  Compound 669 

Moisture    Coatings    677 

New  York  Subway 679 

Novoid    Compound     670 

Oil  and  Paraffin   Washes   .677 

Star  Stellen    Cement 669 

Sylvester  Mortar 675 

Sylvester  Wash    673 

Szerelmey    Wash 673 

Wheelbarrows 

Loads   for    , 47 


OF  THE 

UNIVERSITY 


, 


MIXING  BY  KNEADING 

(THE  STATEMENT  OF  A  PRINCIPLE) 

THE  Chicago  Improved  Cube  Mixer  mixes  concrete  by  a 
kneading  process.     The  charge  of  cement  sand  and  stone 
is  held  together  as  a  unit  and  the  separate  materials  are  in- 
corporated by  a  folding  and  pressing  process  into  a  homogeneous 
batch  of  mixed  concrete.    All  the  materials  are  charged  as  a  unit, 
all  are  mixed  as  a  unit ;  all  are  discharged  as  a  unit.     Segregation 
is  impossible  because  at  no  time  during  the  whole  process  of 
charging,  mixing  and  discharging  is  any  part  or  particle  of  the 


batch  cut  away  from  the  other  parts.  On  the  contrary  every 
motion  of  the  machine  acts  to  keep  together  all  the  particles,  ac- 
complishing the  mixing,  not  by  cutting  and  spooning,  but  by 
folding,  squeezing  and  rubbing  the  cement  paste,  sand  and  ag- 
gregate into  intimate  contact.  This  is  the  cube  principle  of 
mixing  concrete.  To  this  principle  in  its  perfect  development 
the  Chicago  Improved  Cube  mixer  adds  mechanical  perfection  as 
a  mixing  machine — rapid  operation,  minimum  power  consump- 
tion, and  large  output  per  man  worked. 

The  CUDC  orinciDie  of  mixinir  produces  the  most  perfect  concrete  (hat  can  be  mixed — The 
Chicago  Im7rSvedfl.be  Mixer  |i"es  t.ie  cube  principle  in  all  its  perfection  plus  h.2h  output 
and  low  cost  as  a  working  mechanism. 

Municipal  Engineering  &  Contracting  Co. 


NEW  YORK  OFFICE 
90  West  Street 


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Railway  Exchange,  Chicago,  III. 


CONCRETE  AND  REINFORCED 
CONCRETE  CONSTRUCTION. 

By 
HOMER  A.  REID,  ASSOC.M.  AM.  SOC.  C.  E. 


(HIS  is  the  most  complete  and  comprehen- 
sive book  ever  written  on  this  subject.  It 
is  in  fact  a  combination  of  several  books 
in  one — all  original,  carefully  written  and 
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cluding shops,  roundhouses,  etc.  It  has  more  text 
pages,  more  drawings  and  more  tables  of  test  data 
on  concrete  and  reinforced  concrete  construction 
than  any  other  book  ever  published.  No  other  book 
on  concrete  contains  one  tenth  so  much  of  the  very 
latest  data  on  tests,  theory  and  practice.  A  16- 
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In  a  two-column  review  of  this  book,  "Manu- 
facturers' Record"  says:  "There  seems  to  be  no 
portion  of  concrete  or  reinforced  concrete  that  has 
not  been  touched  upon,  and  the  thoroughness  and 
carefulness  with  which  the  author  has  handled  his 
subject  should  make  it  a  valuable  assistant  to 
engineers,  architects,  contractors  and  those  inter- 
ested in  concrete  generally." 

Cloth,  906  pages,  7 1 5  illustrations,  70  tables ;  price  $5  net,  postpaid. 


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Speed  Means  Dollars 

in  all  construction  operations  but  never 
more  so  than  in  the  mixing  of  concrete. 

The  Smith  Mixer 

JTT  Delivers    concrete    so    fast    that    the    builder's 

J\  greatest  problem  is  how  to  get  the  material  to 

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Contractors'  Supply  and  Equipment  Company 

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Branches    in    all    Principal  Citie* 


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11,000  ctes  "Cost  Data" 

Were  sold  last  year  and  the  demand  continues  to  increase. 

This  book  has  over  600  pages  of 
actual  costs  taken  from,  the  private 
records  of  engineers  and  contractors 
and  so  itemized  and  analyzed  as  to 
be  of  inestimable  value  to  any  person 
who  has  to  do  with  making  bids  and 
estimates  or  in  checking  estimates. 
It  gives  also  valuable  data  on  meth- 
ods of  construction,  thus  enabling 
foremen  to  handle  work  in  the  most 
economical  manner  possible. 

The  different  sections  are:  (1) 
Cost-Keeping,  Preparing  Estimates, 
Organization  of  Forces,  etc.;  (2)  Cost 
of  Earth  Excavation;  (3)  Cost  of 
Rock  Excavation,  Quarrying  and 
Crushing;  (4)  Cost  of  Roads,  Pave- 
ments and  Walks;  (5)  Cost  of  Stone 
Masonry ;  (6)  Cost  of  Concrete  Con- 
struction of  All  Kinds;  (7)  Cost  of 
Water  Works;  (8)  Cost  of  Sewers, 
Vitrified  Conduits  and  Tile  Drains ; 
(9)  Cost  of  Piling,  Trestling  and  Tim- 
benvork ;  (10)  Cost  of  Erecting  Build- 
ings; (11)  Cost  of  Steam  and  Elec- 
tric Railways;  (12)  Cost  of  Bridge 
Erection  and  Painting;  (13)  Cost  of 
Railway  and  Topographic  Surveys; 
(14)  Cost  of  Miscellaneous  Structures. 

Flexible  leather,  gilt  edges,  622  pages,  illustrated, 
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George  P.  Carver 

A.  M.  Am.  Soc.  C.  E. 

CONCRETE 
SPECIALIST 

I  am  prepared  to  undertake 
the  designing,  inspection  and 
supervision  of  Reinforced  Con- 
crete Structures  according  to  the 
best  practice;  also  to  submit 
estimates,  specifications  and 
contracts  for  this  class  of  work. 
I  will  act. in  an  advisory  capac- 
ity on  this  form  of  construction. 

REFERENCES  GIVEN 

Telephone  Main  3847 

Exchange  Bldg.  53  State  Street 
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Meacham  &  Wright 
Company 

CEMENT 


Chicago 


WALTER  A.  SHAW,  President,  M.  W.  S.  E. 
JAMES  M.  CORBETT,  Secretary. 
JOSEPH  E.  BIDWILL,  Treasurer. 

Office  Tel  Main  497 

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"Cement"  covers  the  entire  field. 

The  important  literature  that  points  the  way  to  successful  completion  of  concrete 
construction. 

Below  are  a  few  articles  that  have  appeared  in  "Cement"  and  which  suggest  its  value 
to  those  interested : 

"An  Experimental  Study  of  Reinforced  Concrete  in  Compression." 

"Compressive  Resistance  of  Concrete  Reinforced  Laterally." 

"Bowstring  Trusses  of  Reinforced  Concrete." 

"The  Progress  in  Building  Flat,  Solid  Arches  of  Long  Span." 

"The  Adhesion  of  Mortar  and  Concrete." 

"Austrian  Government  Regulations  for  Concrete  and  Reinforced  Concrete  Construction." 

"The  Shearing  Resistance  of  Reinforced  Concrete." 

"The  Determination  of  the  Sliding  Resistance  in  Reinforced  Concrete  Beams." 

"The  Adhesion  of  Concrete  to  Steel  as  Affected  by  the  Quantity  of  Water  Used  in  Mixing." 

"The  Design  of  Reinforced  Concrete  Beams  from  the  Economic  Point  of  View." 

"Bending  Moments  in  Continuous  Reinforced  Concrete  Beams." 

"Surfaces  of  Greatest  Shearing  Stresses  for  Steel  Reinforcing  in  Concrete." 

"The  Compressive  Resistance  of  Blocks  and  Columns  of  Concrete  and  Stone." 

"Table  of  Dimensions  and  Allowed  Working  Stresses  of  Hinged  Concrete  Arches." 

The  designing  engineer,  architect  and  builder  will  find  information  of  a  technical  nature 
that  makes  "Cement"  practically  a  ha.id-book  for  ready  reference. 

Other  articles  on  the  manufacture  of  cement  and  the  progress  of  the  development  of  the 
industry  complete  the  literature  on  the  subject. 

"Cement"  is  published  monthly  by 

The  Progress  Publishing  Co. 


Subscription  $2.00  a  year. 


13=21  Park  Row,  New  York  City 


Practical    Cement 
Testing 

By  W.  PURVES  TAYLOR,  M.  E.,  C.  E. 
Engineer  in  charge  Philadelphia  Municipal  Testing  Laboratories. 

Cloth,  6x9  inches,  330  pages;  142  illustrations:  08  tables; 
$3.00  net,  postpaid. 

This  is  the  first  practical  and  exhaustive  treatise  on  this  important  subject.  It  has 
already  been  adopted  as  a  text  book  by  the  University  of  Pennsylvania  and  leading 
technical  schools.  Each  chapter  contains  a  minute  description  of  the  methods  followed 
in  the  author's  laboratory  and  many  valuable  suggestions  as  to  the  "how"  and  "why" 
of  cement  testing.  The  observation  on  the_  interpretation  of  results,  one  of  the  most 
difficult  tasks  of  the  novice,  are  especially  pertinent  and  are  expressed  in  a  fair  and  con- 
servative manner. 

The  book  is  so  complete  that  it  can  be  put  in  the  hands  of  a  young  engineer  with  con- 
fidence that  it  will  enable  him  to  make  reliable  tests  on  cement.  The  wealth  of  photo- 
graphs and  line  cuts  furnish  the  pictorial  examples  of  how  to  conduct  cement  tests,  and 
the  300  pages  of  text  are  so  explicit  that  even  the  most  inexperienced  men  can  soon  learn 
the  art  of  cement  testing.  Yet  the  book  has  not  a  superfluous  paragraph.  The  list  of 
chapters  includes:  (1)  Classification  and  Statistics,  (2)  Composition  and  Constitution, 
(3)  Manufacture,  (4)  Inspection  and  Sampling,  (5)  The  Testing  of  Cement,  (6)  Specific 
Gravity,  (7)  Fineness,  (8)  Time  of  Setting,  (9)  Tensile  Strength,  (10)  Soundness,  (11)  Chem- 
ical Analysis,  (12)  Special  Tests,  (18)  Approximate  Tests,  (14)  Practical  Operation,  (15) 
Other  Varieties  of  Cement  Than  Portland,  (16)  Specifications  (The  Author's  Am.  Soc.  C.  E., 
A.  M.,  Soc.  Test.  Mtls.,  Soc.  Chem.  Indust.,  Corps  Eng.  U.  S.  A.  British  Standard  Can. 
Soc.  C.  E.). 


Cements,  Mortars  ^ 


—  Their    Physical    Properties 

An  up-to-date  compendium  of  reliable  tests  of  Cements, 
Mortars  and  Concretes 

By  MYRON  S.  FALK,  Ph.  D., 
Instructor  in  Civil  Engineering,  Columbia  University. 

Cloth,  6  x  9  inches;  184  pages;   illustrated;   price,  $2.50  net,  postpaid. 

This  book  contains  a  very  complete  report  of  the  results  of  tests  made  during  the  past 
fifteen  years,  and  gives  these  results  in  tables  and  diagrams  classified  according  to  subjects. 
This  is  a  reference  book  that  should  be  in  the  library  of  every  civil  engineer.  The  contents 
include  chapters  on  Chemical  Properties  of  Cement,  Physical  Tests  of  Cement,  General 
Physical  Properties,  Elastic  Properties  in  General,  Tensile  Properties,  Compressive  Prop- 
erties, Flexural  Properties,  Report  on  Uniform  Tests  of  Cement  by  the  Special  Committee 
of  the  American  Society  of  Civil  Engineers  and  Constitution  of  Cement. 

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FIELD  SYSTEM. 

By  FRANK  B.  QILBRETH. 

This  book  was  written  by  one  of  the  largest  general  contractors 
in  the  world,  and  contains  nearly  200  pages  of  rules  and  instruc- 
tions for  the  guidance  of  his  foremen  and  superintendents.  It  is 
the  outgrowth  of  over  20  years  of  experience  in  the  contracting 
business  and  embodies  scores  of  suggestions  for  economizing  and 
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is  the  contractor  who  made  the  "Cost-plus-a-fixed-sum-con tract" 
famous;  in  doing  so,  he  has  likewise  made  famous  Gilbreth's  "Field 
System,"  only  a  few  excerpts  from  which  have  heretofore  appeared 
in  print. 

In  making  public  his  "Field  System,"  Mr.  Gilbreth  is  performing  a  service 
to  the  public  that  is  comparable  with  the  action  of  a  physician  in  disclosing 
the  secret  of  his  success  in  curing  a  disease.  The  disease  that  Gilbreth's 
"Field  System"  aims  to  cure  is  the  hit  or  miss  method  of  doing  contract  work. 
200  pages,  with  illustrations ;  bound  in  leather ;  price  $3.00  net,  postpaid. 

[In  preparation  April,  1908.     Ready  soon.] 

THEORY  and  DESIGN  of  REINFORCED  CONCRETE  ARCHES 

By  ARVID  REUTERDAHL,  SC.  B.,  A.  M., 

Assistant  City  Engineer,  Spokane,  Wash. 

Of  ail  the  problems  in  bridge  designing  the  analysis  of  the 
elastic  arch  is  by  far  the  most  difficult.  The  works  which  have 
heretofore  appeared  on  this  subject  are  either  so  mathematically 
abstruse  or  leave  so  much  to  the  reader  to  demonstrate  for  himself 
that  they  are  of  little  value  to  the  practical  engineer  or  to  the 
technical  student  whose  mathematical  training  has  not  been  of 
exceptional  order.  This  book  remedies  these  faults.  The  analysis 
is  graphical.  Every  principle  involved  is  explained  thoroughly; 
there  are  no  missing  steps.  The  result  is  for  the  first  time  a 
treatise  on  the  elastic  arch  which  can  be  read  and  understood  by 
the  general  practitioner. 

ENGINEERS'  POCKETBOOK  OF  REINFORCED  CONCRETE 

By  E.  LEE  HEIDENRICH, 

Consulting  Concrete  Engineer. 

This  book  gives  all  the  tables,  formulae  and  data  necessary 
for  the  design  of  reinforced  concrete  structures  of  all  kinds.  Its 
purpose  is  to  do  for  the  reinforced  concrete  engineer  what  Kent 
and  other  pocketbooks  do  for  the  mechanical  or  the  electrical 
engineer.  Design  and  construction  are  all  given  careful  and  ade- 
quate consideration.  Buildings,  Conduits,  Retaining  Walls,  Tanks 
and  Bins,  Bridges  and  Culverts,  etc.,  are  all  covered  by  the  text, 
formulae  and  data.  The  tables  are  numerous  and  practical,  and 
many  of  them  have  been  computed  for  this  book  and  are  not  to 
be -found  elsewhere. 
Flexible  leather,  about  300  pages,  illustrated;  price,  $3.00  net,  postpaid. 

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cement-concrete  products  industry — because  it  gives,  in 
each  issue,  more  up-to-date  authentic  information  on  live 
subjects  pertaining  thereto,  than  any  similar  publication. 

Its  News  Departments  present  the  latest  details  as  to 
new  companies  projected  and  organized — being  carefully 
compiled  from  authentic  sources  and  as  nearly  accurate  as 
such  news  can  be  made. 

Special  Subjects  of  timely  interest  and  value  appear 
in  each  number,  keeping  the  reader  posted  as  to  the  most 
recent  and  important  developments  in  the  field  at  large, 
prepared  by  writers  of  practical  knowledge  and  well-known 
ability.  

It  is  therefore  the  Best  Paper  for  those  desiring  to 
keep  fully  ported  as  the  cement-concrete  industry  in 
general,  as  well  as  these  looking  for  specific  information  on 
Special  Subjects. 

IW"  The  perusal  of  its  columns  will  prove  of  practical 
value  to  the  manufacturer,  or  prospective  manufacturer  of 
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ROCK  EXCAVATION-METHODS  AND  COST. 

BY 

HALBERT   P.  GILLETTE, 

Editor  ' ' Engineering-Contracting. 

This  book  covers  the  whole  subject  of  rock  excavation, 
whether  in  excavations  for  structures  or  in  quarries.  Tunneling, 
shaft  sinking  and  quarrying  and  crushing  are  considered  in  par- 
ticular detail.  It  is  a  practical  book  for  practical  rock  men. 
One  superintendent  who  purchased  this  book  writes  that  he  has 
cut  the  cost  of  his  drilling  and  blasting  practically  in  half  since 
he  received  the  book  and  applied  the  methods  given  by  Mr.  Gil- 
lette. "Rock  Excavation"  has  chapters  describing: 

Rocks  and  Their  Properties— Methods  and  Cost  of  Hand  Drilling- 
Machine  Drills  and  Their  Use — Steam  and  Compressed  Air  Plants — The 
Cost  of  Machine  Drilling — Cost  of  Diamond  Drilling — Explosives — Charg- 
ing and  Firing — Methods  of  Blasting — Cost  of  Loading  and  Transporting 
Rock: — Quarrying  Stone — Open  Cut  Excavation — Methods  and  Cost  on 
the  Chicago  Drainage  Canal — Cost  of  Trenches  and  Subways — Subaque- 
ous Excavation — Cost  of  Railway  Tunnels — Cost  of  Drifting,  Shaft  Sink- 
ing and  Stoping. 

Cloth,  5^x7  inches,  384  pages,  56  figures  and  illustrations;  $3. 00  net, 
postpaid. 

EARTHWORK  AND  ITS  COST. 

BY 

HALBERT   P.  GILLETTE, 

Editor  ' ' Engineering-Contracting" 

A  book  that  should  be  in  the  hands  of  every  man  who  is  in 
charge  of  "moving  dirt,"  whether  with  pick  and  shovel,  plow 
and  scraper,  steam  shovel  and  dredge,  or  any  other  tool  for  dig- 
ging and  conveying  earth. 

Cloth,  5x7£  inches,  260  pages,  50  figures  and  illustrations ;  $2.00  net, 
postpaid. 

ECONOMICS  OF  ROAD  CONSTRUCTION. 

BY 

HALBERT   P.  GILLETTE, 

Editor  ' ' Engineering-Contracting. ' ' 

This  book  is  the  only  book  on  road  construction  that  goes 
into  the  detailed  cost  of  construction.  The  methods  and  cost 
of  construction  given  are  drawn  from  the  author's  own  expe- 
rience, both  as  an  engineer  in  charge  of  road  work  and  as  a  con- 
tractor for  constructing  many  miles  of  roads  of  all  kinds. 
Cloth,  184  pages,  illustrated  ;  price  $1.00  net,  postpaid. 


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JUST    A    MINUTE! 

After  you  have  read  Mr.  Gillette's  book  on  Concrete  Con- 
struction-Methods and  Cost  you  will  find  the  Handbook  for  Cement 
Users,  by  Charles  Carroll  Brown,  M.  Am.  Soc.  C.  E.,  a  very  neces- 
sary addition  to  your  books  on  concrete.  The  Handbook  contains 
much  information  that  you  will  find  helpful,  such  as  a  collection 
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various  kinds  of  concrete  and  methods  of  placing.  The  Handbook 
meets  all  the  needs  of  the  practical  Engineer  and  Constructor  not 
met  by  Mr.  Gillette's  book.  The  two  together  will  make  a  com- 
plete library  on  practical  Concrete  Construction.  It  contains  368 
pages,  bound  in  cloth.  Price,  $3.00,  carriage  prepaid. 

The  Directory  of  American  Cement  Industries 

A  complete  directory  of  the  great  modern  industry  in  all  its 
branches.  Contains  lists  of  manufacturers  of  cement,  trade  brands, 
dealers,  sales  agents,  contractors  and  other  users  of  cement,  manu- 
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reliable  credit  ratings  and  approximates  the  amount  of  cement 
handled  by  each  party.  Kept  up  to  date  by  frequent  new  addi- 
tions. 650  pages,  cloth.  $5.00,  carriage  prepaid. 

Municipal  Engineering  Magazine 

The  leading  authority  on  the  manufacture  and  use  of  cement 
in  America.  The  pioneer  publication  in  the  development  of  the 
industry.  Every  number  adds  to  the  stock  of  knowledge  in  the 
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by  its  title  and  will  serve  to  keep  the  Engineer  and  Contractor  up 
to  date.  More  than  800  pages  in  a  year  for  $2.00. 

Send  all  orders  for  books  and  the  magazine  to 

Municipal  Engineering  Co. 
Commercial  Club  Bldg.  Indianapolis,  Ind. 


Engineering=Contracting 

EVERY  WEDNESDAY    9  1    FOR  THE  52  ISSUES 

This  is  the  great  METHODS  AND  COST  paper, 
and  is  the  only  engineering  paper  published  whose 
editor  has  had  actual  contracting  experience  and 
who  is  at  the  same  time  a  practicing  engineer.  It 
is  devoted  to  the  interest  of  the  engineer  as  a 
builder,  and  its  articles  deal  with  those  practical 
features  which  enable  engineers  and  contractors 
to  make  close  and  accurate  estimates  and  foremen 
to  handle  work  in  the  most  economical  manner 
possible.  The  information  concerning  costs  is  not 
contract  prices,  but  actual  costs  taken  from  the 
private  records  of  engineers  and  contractors,  and 
so  itemized  and  analyzed  as  to  be  of  inestimable 
value  to  any  person  who  has  to  do  with  making 
bids  and  estimates  or  in  checking  estimates  on 
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Articles  showing  the  methods  and  cost  of  con- 
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various  classes  of  work  are  published  each  week; 
also  articles  giving  the  actual  cost  of  erecting  con- 
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ence encyclopedia  on  methods  and  costs. 

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